Question

The function f(x) = 0.12x + 11 relates how much John pays for mobile service, f(x), to the number of minutes, x, used for local calls in a month. What is the value and meaning of f(220)?

Answer 1

x represents the number of minutes. In this equation, you simply plug in 220 for x and add 11 (the fee or initial cost).
f(x) = 0.12x + 11
f(220) = 0.12(220) + 11
f(220) = 37.4

Therefore, John pays a total of $37.40 in a month.