Math
posted by Andrea .
According to a rating agency, a car's MPG (miles per gallon) ratings are: 25 MPG for city and 30 MPG for highway driving. A driver spent $20.00 (the gasoline costs $1.25/gallon) on a combined city and highway trip of 450 miles. How many miles "C" in city and "H" on highway was the car driven ?
I need to put this into 2 equations. How does the $20.00 fit into the equation?

<<How does the $20.00 fit into the equation? >>
Let C = city miles and H = highway miles
City gas cost + Highway gas cost = $20
(C/25)*1.25 + (H/30)*1.25 + 20
0.05 C + 0.04167 H = 20
Combine that with
C + H = 450
to get the answer.
C + 0.8333 H = 400
.16667 H = 50
H = 300 miles
C = 150 miles