Question

A rental car company $40 per day plus $0.20 for each mile the rental car is driven if a customer gives the rental gives the rental attendant $100 for a charge of $56 how many miles did the customer drive

Answer 1

if the charge is $56, what does it matter how much he gave to the attendant?
To drive m miles in one day, the charge is 40 + 0.20m

so you just need to solve
40 + 0.20m = 56