Hans purchased a prepaid phone card for $45.50. Calls cost
7 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)=45.50-0.07x
How much credit is left on the card after Hans uses it for
30 minutes of calls?
just substitute in 30 for x and evaluate the number.
To find out how much credit is left on the card after using it for 30 minutes of calls, we can substitute x = 30 into the function C(x) = 45.50 - 0.07x and solve for C(30).
C(x) = 45.50 - 0.07x
C(30) = 45.50 - 0.07 * 30
Now let's calculate it step by step:
C(30) = 45.50 - 0.07 * 30
C(30) = 45.50 - 2.10
C(30) = 43.40
Therefore, after using the card for 30 minutes of calls, there will be $43.40 credit left on the card.