To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}11\\ -\ 10\end{array}}{ \ \ \ \ \ \space 1}$

We can start at $\displaystyle 11$ and count back $\displaystyle 10$.

$\displaystyle 11,10,9,8,7,6,5,4,3,2,1$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}12\\ -\ 10\end{array}}{ \ \ \ \ \ \space 2}$

We can start at $\displaystyle 12$ and count back $\displaystyle 10$.

$\displaystyle 12,11,10,9,8,7,6,5,4,3,2$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}13\\ -\ 10\end{array}}{ \ \ \ \ \ \space 3}$

We can start at $\displaystyle 13$ and count back $\displaystyle 10$.

$\displaystyle 13,12,11,10,9,8,7,6,5,4,3$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}14\\ -\ 10\end{array}}{ \ \ \ \ \ \space 4}$

We can start at $\displaystyle 14$ and count back $\displaystyle 10$.

$\displaystyle 14,13,12,11,10,9,8,7,6,5,4$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}15\\ -\ 10\end{array}}{ \ \ \ \ \ \space 5}$

We can start at $\displaystyle 15$ and count back $\displaystyle 10$.

$\displaystyle 15,14,13,12,11,10,9,8,7,6,5$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}16\\ -\ 10\end{array}}{ \ \ \ \ \ \space 6}$

We can start at $\displaystyle 16$ and count back $\displaystyle 10$.

$\displaystyle 16,15,14,13,12,11,10,9,8,7,6$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}17\\ -\ 10\end{array}}{ \ \ \ \ \ \space 7}$

We can start at $\displaystyle 17$ and count back $\displaystyle 10$.

$\displaystyle 17,16,15,14,13,12,11,10,9,8,7$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}18\\ -\ 10\end{array}}{ \ \ \ \ \ \space 8}$

We can start at $\displaystyle 18$ and count back $\displaystyle 10$.

$\displaystyle 18,17,16,15,14,13,12,11,10,9,8$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}19\\ -\ 10\end{array}}{ \ \ \ \ \ \space 9}$

We can start at $\displaystyle 19$ and count back $\displaystyle 10$.

$\displaystyle 19,18,17,16,15,14,13,12,11,10,9$

To find the missing piece of an addition problem, we can take the biggest number minus the smallest number. 

$\displaystyle \frac{\begin{array}[b]{r}11\\ -\ 10\end{array}}{ \ \ \ \ \ \space 1}$

We can start at $\displaystyle 11$ and count back $\displaystyle 10$.

$\displaystyle 11,10,9,8,7,6,5,4,3,2,1$