Answer:
answer is red (C=15+0.2x)
Step-by-step explanation:
No matter how long your airtime usage is, it will at least cost $15 per month and you have to pay $0.20 per minute/s.
Formula would be (C=15+0.2x)
An example, if she uses 5 minutes of airtime then the equation will be;
C=15+(0.2×5)
C=15+1
C=16
