Answer:
Johnson's made 80 minutes of local calls
Step-by-step explanation:
The Johnson's pay $9.95 a month plus $0.035 per min for local phone service.
i.e. if Johnson's makes a local phone call for m minutes in a month then, monthly payment they have to make equals
$(9.95+0.035m)
Last month, they paid $12.75.
Let they made m minutes of local calls
then, 9.95+0.035m=12.75
0.035m=12.75-9.95
0.035m=2.8
m=2.8/0.035
m=80
Hence, Johnson's made 80 minutes of local calls
