Question

if f(x)= -x+7 what is f(15)?

Answer 1

x = 15

Substitute that to equation

-(15) + 7

Answer:
f(x) = -8

Answer 2

F(x)=-x+7, and by saying “f(15)”, your saying x=15, since f(x) turns into f(15). So just replace all x’s with 15.

F(15)=-15+7
F(15)=-8

So -8 is the answer:)