Nice work on answering parts (a) and (c) correctly.
I'll go over part (b) only.
We replace the C(m) with 95.16 to form the equation
95.16 = 27 + 0.12m
You have the correct equation set up. Your teacher wants you to solve for m.
So,
95.16 = 27 + 0.12m
95.16-27 = 0.12m
68.16 = 0.12m
0.12m = 68.16
m = 68.16/0.12
m = 568
If the student uses exactly 568 minutes, then the cost will be $95.16
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Check:
C(m) = 27 + 0.12m
C(568) = 27 + 0.12*568
C(568) = 27 + 68.16
C(568) = 95.16
The answer is confirmed.
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Answer: 568
