The johnsons pay $9.95 a month plus $.035 per min for local phone service. Last month, they paid $12.75. How many minutes of local calls did they make?

Answer : The Johnson's used 8 minutes of local calls.

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