A)
a = 20m + 12
b = 22m
B)
Set the equations equal since you want to know when the costs are the same:
22m = 20m + 12
C)
Solve:
Subtract 20m from both sides of the equation, thus combining all the like-term variables on the same side of the equals sign.
2m = 12
Divide both sides if the equation by the coefficient of m, which is 2 in this case.
m = 6
So, the costs will be the same after 6 months.