Line the numbers up, one above the other.  Add 4 and 5 to get 9.  Add 2 and 3 to get 5.  The answer is 59.

First, identify which number is in the hundreds place.  The hundreds place is 3 places to the left of the decimal.  In this case, 3 is in the hundreds place.

If the numbers to the right of the 3 are 50 or more, then we will round it up to 4.  If they are less than 50, we will leave the 3 the same.  Here, we have 42, so the 3 will remain the same.  The two numbers to the right become zeroes.

We round 342 down to 300.  The 2 in the thousands place remains the same.

To find out what number to subtract 0.7 from to get 2.8, just do the opposite - add 0.7 to 2.8.

\(\displaystyle 0.7+ 2.8 = 3.5\)

The least number is 1, followed by 3, then 6 and finally, 7.

\(\displaystyle \fn_cm \fn_cm Line\;up\;the\;numbers\;and\;add\;straight\;down.\)

    \(\displaystyle 100\)

\(\displaystyle \underline{+350}\)

    \(\displaystyle 450\)

\(\displaystyle x-35=135\)

    \(\displaystyle \underline{+35\;\;\;+35}\) 

  \(\displaystyle x=135+35\)

   \(\displaystyle \fn_cm 1\not{3}^{4}\: 5\)

  \(\displaystyle \fn_cm \fn_cm \fn_cm \underline{+\;\;3\;5}\)

     \(\displaystyle 1\: 7\: 0\)

\(\displaystyle 5+5=10\rightarrow \;Carry\;the\;1.\;Add\;the\;1\;to\;the\;3\;in\;1\underline{3}5.\)

\(\displaystyle 4+3=7\)

\(\displaystyle 1+0=1\)

\(\displaystyle \fn_cm \fn_cm \fn_cm \fn_cm Line\;up\;the\;numbers\;and\;add\;straight\;down.\)

\(\displaystyle 5+\, 9=14\)

\(\displaystyle \fn_cm Carry\;the\;1\;from\;the\;\underline{1}4.\;Add\;the\;1\;to\;the\;0\;in\;205.\)

\(\displaystyle 1+0=1\)

\(\displaystyle 2+0=2\)

    \(\displaystyle \fn_cm 2\not{0}^{1}\: 5\)

 \(\displaystyle \fn_cm \fn_cm \fn_cm \fn_cm \fn_cm \fn_cm \fn_cm \underline{+\;\;\;\;\;\;\: 9}\)   

     \(\displaystyle \fn_cm \fn_cm 2\;\;1\: 4\)    

Line up the numbers vertically. Add the ones place first \(\displaystyle (5+9=14)\). Keep the 4, carry the 1. Then add the 3 digits in the tens place \(\displaystyle (1+3+4 = 8)\). Keep the 8. Then add the hundreds place \(\displaystyle (7+5=12)\). The sum is 1284

One quarter is \(\displaystyle 25\cent\), one dime is \(\displaystyle 10\cent\), and one nickel is\(\displaystyle 5\cent\).

Three quarters is \(\displaystyle 75\cent\), 2 dimes is \(\displaystyle 20\cent\), and one nickel is \(\displaystyle 5\cent\). If you add these three values you get \(\displaystyle \$1\).

To find the sum, you need to add. Line up all numbers vertically. Since one number has a decimal to the tenths place, one has a decimal to the hundredths place, and one has no decimal, be extra careful to line up the digits correctly! To help you, add a zero to the end of 2.4, and add two zeroes to the end of 55 so that all the digits line up correctly.

\(\displaystyle \begin{matrix} &\ 2.40 \\ & 55.00\\ + & \ 6.21 \end{matrix}\)

Now, add down each column, starting on the right side and moving to the left.

\(\displaystyle 2.40 + 55.00+ 6.21 = 63.61\)

The sum is 63.61.