Let f(x) be a linear function with f(1) = 2 and f(3) = 8. Find f(5)

Question

How do u solve it like the steps

Answer 1

f changes by 6 when x changes by 2, so the slope is 6/2 = 3.

So, f(x) = 3x+b

Since f(1)=2, b = -1

f(x) = 3x-1

Answer 2

Would the answer be 16?

Answer 3

Cause if f(x)=3x-1
F(5) would be 3(5)-1
Which is 14
But someone told me the answer was 16

Answer 4

someone might be wrong