Pre-Algebra : Two-Step Equations

Study concepts, example questions & explanations for Pre-Algebra

varsity tutors app store varsity tutors android store

Example Questions

Example Question #1 : Two Step Equations

Solve for \displaystyle x:

\displaystyle 4x+3=7

Possible Answers:

\displaystyle 1

\displaystyle -1

\displaystyle 4

\displaystyle -4

Correct answer:

\displaystyle 1

Explanation:

The goal is to isolate the variable to one side.

\displaystyle 4x+3=7

Subtract \displaystyle 3 from each side of the equation:

\displaystyle 4x+3-3=7-3

\displaystyle 4x=4

Divide each side by \displaystyle 4:

\displaystyle \frac{4x}{4}=\frac{4}{4}

\displaystyle x=1

Example Question #2 : Two Step Equations

Solve for \displaystyle x:

\displaystyle 6x^{2}=216

Possible Answers:

\displaystyle \pm 6

\displaystyle 6

\displaystyle \pm 3

\displaystyle \pm 9

Correct answer:

\displaystyle \pm 6

Explanation:

The goal is to isolate the variable to one side.

\displaystyle 6x^{2}=216

Divide each side by \displaystyle 6:

\displaystyle \frac{6x^{2}}{6}=\frac{216}{6 }

\displaystyle x^{2}= 36

Take the square root of each side:

\displaystyle \sqrt{x^2}=\sqrt{36}

\displaystyle x=\pm 6

Example Question #3 : Two Step Equations

Solve for \displaystyle x:

\displaystyle 3x^{^{3}}+4=28

Possible Answers:

\displaystyle 7

\displaystyle 2

\displaystyle -2

\displaystyle -7

Correct answer:

\displaystyle 2

Explanation:

The goal is to isolate the variable to one side.

\displaystyle 3x^{^{3}}+4=28

Subtract \displaystyle 4 from each side:

\displaystyle 3x^{^{3}}+4-4=28-4

\displaystyle 3x^{^{3}}=24

Divide each side by \displaystyle 3:

\displaystyle \frac{3x^{^{3}}}{3}=\frac{24}{3}

\displaystyle x^3=8

Take the cube root of each side:

\displaystyle \sqrt[3]{x^3}=\sqrt[3]{8}

\displaystyle x=2

Example Question #4 : Two Step Equations

Solve for \displaystyle x:

\displaystyle x^2+20=45

Possible Answers:

\displaystyle \pm5

\displaystyle \pm15

\displaystyle 5

\displaystyle 10

Correct answer:

\displaystyle \pm5

Explanation:

The goal is to isolate the variable to one side.

\displaystyle x^2+20=45

Subtract \displaystyle 20 from each side:

\displaystyle x^2+20-20=45-20

\displaystyle x^2=25

Take the square root of each side:

\displaystyle \sqrt{x^2}=\sqrt{25}

\displaystyle x=\pm5

Example Question #2 : Two Step Equations

Solve for \displaystyle x.

\displaystyle 2x+5=19

Possible Answers:

\displaystyle 12

\displaystyle 9

\displaystyle 24

\displaystyle 14

\displaystyle 7

Correct answer:

\displaystyle 7

Explanation:

Step 1: Subtract \displaystyle 5 from both sides:

\displaystyle 2x+5-5=19-5

\displaystyle 2x+0=14

\displaystyle 2x=14

Step 2: Divide both sides by \displaystyle 2:

\displaystyle \frac{2x}{2}= \frac{14}{2}

\displaystyle x=7

Example Question #3 : Two Step Equations

\displaystyle 4x -3=33

Possible Answers:

\displaystyle -3

\displaystyle 9

\displaystyle 3

\displaystyle 10

Correct answer:

\displaystyle 9

Explanation:

To solve two-step equations, first move everything that does not have the variable over to the other side of the equation. In order to move the -3 to the other side of the equation, you must do the opposite operation (addition). Keep in mind you must do the same step on each side of the equation every time you change something.

\displaystyle 4x-3=33

      \displaystyle +3=+3

The equation should now look like this:

\displaystyle 4x=36

Next, isolate the variable by moving it to the other side of the equation. Do this by doing the opposite operation (division):

\displaystyle \frac{4x}{4}=\frac{36}{4}=9

The result should be the following:

\displaystyle x=9

Example Question #4 : Two Step Equations

\displaystyle 7x -2 =47

Possible Answers:

\displaystyle 9

\displaystyle 6

\displaystyle 8

\displaystyle 7

Correct answer:

\displaystyle 7

Explanation:

To solve two-step equations, first move everything that does not have the variable over to the other side of the equation. In order to move the -2 to the other side of the equation, you must do the opposite operation (addition). Keep in mind you must do the same step on each side of the equation every time you change something.

\displaystyle 7x-2=47

      \displaystyle +2=+2

The equation should now look like this:

\displaystyle 7x=49

Then, isolate the variable by moving the 7 to the other side of the equation. Do this by doing the opposite operation (division).

\displaystyle \frac{7x}{7}=\frac{49}{7}=7

The result should be the following:

\displaystyle x=7

Example Question #63 : Algebraic Equations

\displaystyle 15x-38=82

Possible Answers:

\displaystyle 8

\displaystyle 3

\displaystyle 2

\displaystyle 6

Correct answer:

\displaystyle 8

Explanation:

To solve two-step equations, first move everything that does not have the variable over to the other side of the equation. In order to move the -38 to the other side of the equation, you must do the opposite operation (addition). Keep in mind you must do the same step on each side of the equation every time you change something.

\displaystyle 15x-38=82

        \displaystyle +38=+38

The equation should now look like this:

\displaystyle 15x=120

Then, isolate the variable by moving the 15 to the other side of the equation. Do this by doing the opposite operation (division).

\displaystyle \frac{15x}{15}=\frac{120}{15}=8

The result should be as follows:

\displaystyle x=8

Example Question #9 : Two Step Equations With Integers

Solve for x:

\displaystyle 2x+14=58

Possible Answers:

\displaystyle x=23

\displaystyle 2x=44

\displaystyle x=22

\displaystyle \frac{x}{2}=\frac{54}{-14}

\displaystyle x=15

Correct answer:

\displaystyle x=22

Explanation:

In order to find x, you need to isolate it. If x isn't alone, you haven't finished solving the problem! 

Step 1: subtract 14 from both sides of the equation

\displaystyle 2x+14-14=58-14

\displaystyle 2x=44

Step 2: divide both sides of the equation by 2

\displaystyle \frac{2x}{2}=\frac{44}{2}

\displaystyle x=22

Example Question #10 : Two Step Equations With Integers

Solve for x:

\displaystyle -5x+4=-21

Possible Answers:

\displaystyle x=-3\frac{2}5{}

\displaystyle x=6

\displaystyle x=-5

\displaystyle x=-30

\displaystyle x=5

Correct answer:

\displaystyle x=5

Explanation:

Step 1: subtract 4 from both sides

\displaystyle -5x+4=-21

\displaystyle -5x+4-4=-21-4=-25

Step 2: divide both sides by -5 to isolate x

\displaystyle \frac{-5x}{-5}=\frac{-25}{-5}

Solve:

\displaystyle x=\frac{-25}{-5}=5

\displaystyle x=5

 

Remember, a negative integer divided by another negative integer will have a positive answer. 

Learning Tools by Varsity Tutors