Problema Solution
The equation 9+12m=6+15(m-1) models the following situation: Movie-rental company A charges a sign-up fee of $9 plus $12 per month, and company B charges $6 for the first month plus $15 per month after that. At a certain number of months, the cost of the two companies is equal.
Answer provided by our tutors
9+12m=6+15(m-1)
we assume the problem goal is solving for 'm', the number of months at which the cost of the two companies is equal
9+12m=6+15m-15
9 + 12m = 15m - 9
18 = 3m
m = 18/3 = 6
the costs of the two companies are equal after 6 months