Question

Given f(x) = 3x + 4. What is f(8)?

4

8

15

28

Answer 1

you might recognise this more if written
y=3x+4
find y when x=8

Just for info:
f(x) is just a notation to say that 'some function of x'

Answer 2

\(\bf f({\color{red}{ x}}) = 3{\color{red}{ x}} + 4\qquad f({\color{red}{ 8}}) = 3({\color{red}{ 8}}) + 4\)