Answer:
$40
Step-by-step explanation:
If you were to purchase 7 picture frames, you would replace x in the equation with 7, this is shown below.
f(x)=9x-23 ---> f(x)=9(7)-23
Now we can solve for f(x). First start with 9(7).
f(x)=9(7)-23 ---> f(x)=63-23
Now finish the last part by subtracting 23 from 63.
f(x)=63-23 ---> f(x)=40
This means that you would have to pay $40 dollars to purchase the 7 picture frames.