This is a subtraction problem because we want to know how many gifts Sarah has left to open after she's already opened some.

We can start at $\displaystyle 14$ and count back $\displaystyle 9$.

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

$\displaystyle \frac{\begin{array}[b]{r}14\\ -\ 9\end{array}}{ \ \ \ \space 5}$

This is a subtraction problem because some of the friends that Matt invitied did not come, so the total number of people that did come has to be less than what he invited. 

We can start at $\displaystyle 15$ and count back $\displaystyle 7$.

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

$\displaystyle \frac{\begin{array}[b]{r}15\\ -\ 7\end{array}}{ \ \ \ \space 8}$

This is a subtraction problem because some of Mrs. Smith's students are out with the flu, so the number of students in class has to be less than the total number of students that she has. 

We can start at $\displaystyle 18$ and count back $\displaystyle 4$.

$\displaystyle 18,17,16,15,14$

$\displaystyle \frac{\begin{array}[b]{r}18\\ -\ 4\end{array}}{ \ \ \space 14}$

This is a subtraction problem because we want to know how many homework problems Joe will have left after he does some of them, so he will have less than what he started with. 

We can start at $\displaystyle 17$ and count back $\displaystyle 11$.

$\displaystyle 17,16,15,14,13,12,11,10,9,8,7,6$

$\displaystyle \frac{\begin{array}[b]{r}17\\ -\ 11\end{array}}{ \ \ \ \ \ \space 6}$

This is a subtraction problem because we want to know how many extra desks Mr. Bell has after the $\displaystyle 17$ he needs are used. 

We can start at $\displaystyle 20$ and count back $\displaystyle 17$.

$\displaystyle 20,19,18,17,16,15,14,13,12,11,10,9,8,7,6,5,4,3$

$\displaystyle \frac{\begin{array}[b]{r}20\\ -\ 17\end{array}}{ \ \ \ \ \ \space 3}$

This is a subtraction problem because Lisa has alreayd gone to some of the parties that she was invited to, so she has less parties left to go to than she started with this summer. 

We can start at $\displaystyle 7$ and count back $\displaystyle 4$.

$\displaystyle 7,6,5,4,3$

$\displaystyle \frac{\begin{array}[b]{r}7\\ -\ 4\end{array}}{ \ \ \ \ \space 3}$

This is a subtraction problem because people did not show up for practice, so there will be less people at practice than if everyone had shown up. 

We can start at $\displaystyle 18$ and count back $\displaystyle 5$.

$\displaystyle 18,17,16,15,14,13$

$\displaystyle \frac{\begin{array}[b]{r}18\\ -\ 5\end{array}}{ \ \ \space 13}$

This is a subtraction problem because Tiffany lost balloons so she will have less than what she started with. 

We can start at $\displaystyle 11$ and count back $\displaystyle 4$.

$\displaystyle 11,10,9,8,7$

$\displaystyle \frac{\begin{array}[b]{r}11\\ -\ 4\end{array}}{ \ \ \ \space 7}$

This is a subtraction problem because we want to know how many of the total treats Spot has eaten. We take the total number of treats and then subtract the number of treats that are left in the box. $\displaystyle 100-52=48$.

This is a subtraction problem because we want to know how many balls are left over after each boy takes one. We start with the number of balls and then subtract the number that was taken. $\displaystyle 58-11=47$.