Answer:
The answer is 4
Explanation:
f(x)=4x-7
f(x)=9
9=4x-7
9+7=4x-7+7
(the -7 and the +7 cancel out, and remember: whatever you do the one side you have to do to the other)
16=4x
(divide by 4 to isolate x and do the same to the other side of the equation so you get the answer)
so, x=4