Question

Given f(x)=5x+15 find f(x)=30

Answer 1

Given the function, f(x) = 5x + 15:

In order to find the value of x when f(x) = 30, substitute the value of the output into the function:

f(x) = 5x + 15
30 = 5x + 15

Subtract 15 from both sides:
30 - 15 = 5x + 15 - 15

15 = 5x

Divide both sides by 5:
15/5 = 5x/5

x = 3

Therefore, the value of x when f(x) = 30 is 3, or f(3) = 30.