You have the following expression for f(x):
f(x) = 5x - 1
In order to find the value of f(5), replace x = 5 into the previous expression and simplify:
f(5) = 5(5) - 1 = 25 - 1 = 24
Hence, f(5) is 24
To determine the value of x when f(x) = 14, solve for x, as follow:
14 = 5x - 1 add 1 both sides
14 + 1 = 5x
15 = 5x divide by 5 both sides
15/5 = x
3 = x
x = 3
Hence, x = 3 when f(x) = 14