The Science Club needs to rent a bus for a field trip. Main Street Buses charges a $40 rental fee, plus $2 per mile. County Bus Line charges a $20 rental fee, plus $3 per mile. For what number of miles will the total charges be the same? What will that charge be?

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 2*20 is the charge

if your mileage is 50miles, when 2*50 is the charge

if your mileage is 1000miles, when 2*1000 is the charge

if your mileage is "m" miles, when 2*m 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 3*20 is the charge

if your mileage is 50miles, when 3*50 is the charge

if your mileage is 1000miles, when 3*1000 is the charge

if your mileage is "m" miles, when 3*m 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