How much credit is left on the card after Chau uses it for 40 minutes of calls?

Question

Chau purchased a prepaid phone card for $15.00. Calls cost 5 cents a minute using this card. The credit, C (in dollars), left on the card after it is used for x minutes of calls is given by the following function.

C(x)=15.00-0.05x

Answer 1

The question gives us the equation for the credit left on the card after "x" minutes, which is C(x)=15.00-0.05x

For this question, we want to find the credit left on the card after 40 minutes. Therefore, we plug-in "40" for "x" in the equation.

We get, C(40) = 15 - 0.05(40) = 15-2 = 13.

Hope it makes sense.