word problem

Question

A family has two cars. The first car has a fuel efficiency of
35
miles per gallon of gas and the second has a fuel efficiency of
20
miles per gallon of gas. During one particular week, the two cars went a combined total of
1700
miles, for a total gas consumption of
55
gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

let gas consumed by 1st car=x
gas consumed by 2nd car=55-x

 

distance traveled=fuel efficiency*gas consumed

            1700     = 35x + 20(55-x)

            1700     =35x + 1100 -20x

 

            1700     =15x +1100

 

            600      =15x

 

            40       =x

 

gas consumed by 1st car=x   = 40 gal
gas consumed by 2nd car=55-x =55-40=15 gal