M = Main Buses
C = County Buses
so the charges from Main are $40 fee, then additional $2 for every mile you drive it for, so M = 40 + 2m
if your mileage is 20miles, when 220 is the charge
if your mileage is 50miles, when 250 is the charge
if your mileage is 1000miles, when 21000 is the charge
if your mileage is "m" miles, when 2m is the charge
and County charges are $20 fee, then additional $3 for every mile... .so then C = 20 + 3m
if your mileage is 20miles, when 320 is the charge
if your mileage is 50miles, when 350 is the charge
if your mileage is 1000miles, when 31000 is the charge
if your mileage is "m" miles, when 3m is the charge
so, their total charge is M and C respectively
when are the charges equal? well, when M = C
or
40 + 2m = 20 + 3m
solve for "m", to see at how many miles that happens
what will the charge be? plug that value for "m" on either, to get the charge