Its a different type of question.
In a family there are two cars. In a given week, the first car gets an average of 20 MPG, and the second car gets 15 MPG. The two cars combined drive a total of 1000 miles in that week, for a total gas consumption of 60 gallons. How many gallons were consumed by each of the cars that week.
and this is what I did:
x= First car @ 20MPG
y= Second car @ 15MPG
/15 /15 /15