Ok so he had to pay (i'll say 17 because it's easier to type but understand it's 16.99) 17 dollars up front, and he paid 0.88x, x being miles driven. This means for how many miles he's driven, the equation would look like 17 + 0.88x. Set this equal to 203.55 to find out how many miles he drove. Solving this you get 212 miles.