Answer: it will take 2 months.
Step-by-step explanation:
Let x represent the number of months it will take for the total cost for both companies to be equal.
Company A: $80 for a new phone and the monthly fee of $45 a month. This means that the total amount that Company A charges for x months would be
80 + 45x
Company B: she can keep her all sound and pay $85 a month. This means that the total amount that Company B charges for x months would be
85x
For the total cost for both companies to be equal, the number of months would be
80 + 45x = 85x
85x - 45x = 80
40x = 80
x = 80/40 = 2
