Question

A rental car costs a minimum charge plus a fixed charge per mile driven. One customer was charged $60 for 160 miles of use. Another customer drove 280 miles and paid $90. Write an equation relating the total cost, C (in dollars), to the miles driven, x.

Answer 1

Let C = ax + b,

from the data
60 = 160a + b and
90 = 280a + b

solve these two, you should get a=1/4 and b=20

then
C = (1/4)x + 20