Answer:
d. You pay $9 for a burger and some amount for dessert for a total of $16.
Explanation:
We have the following equation:

So the variable of this equation is the amount of money. According to the statement we have that:
- A burger costs $9.
- A dessert costs $x
- The total you pay is $16
If we solve this equation, we have that:

So the dessert costs $7. Finally, you pay $16 for the burger and the dessert as follows:
- You pay $9 for the burger.
- You pay $7 for the dessert.
- You pay a total amount of money = $16