ANSWER :
b. 75 minutes
EXPLANATION :
We can formulate a relation with the cost and minutes :

where y = total cost
x = number of minutes
m = cost per minute of calls
and
b = fixed monthly fee
The first company charges b = $27.95 monthly fee and the rate is m = $0.12 per minute
The equation will be :

The next company charges b = $12.95 a month and the rate is m = $0.32 per minute.
The equation will be :

We are looking for the number of minutes (x) in which the total cost (y) are the same for both companies.
So we can equate y = y

Solve for x :
