Question

A family has two cars. The first car has a fuel efficiency of 40 miles per gallon of gas and the second has a fuel efficiency of 15 miles per gallon of gas. During one particular week, the two cars went a combined total of 1025 miles, for a total gas consumption of 35 gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

I have problem here with just slight changes in the given values, this will help you to solve the problem.

 Distance = Efficiency * Gallons 

First car: 
Distance = x 
Efficiency = 20 
Gallons = x/20 

Second car: 
Distance = 1300 - x 
Efficiency = 15 
Gallons = (1300 - x)/15 

x/20 + (1300 - x)/15 = 75 

3x/60 + 4(1300 - x)/60 = 75 

3x/60 + (5200 - 4x)/60 = 75 

(3x + 5200 - 4x)/60 = 75 

(5200 - x)/60 = 75 

5200 - x = 4500 

x = 700 

First car: 
Gallons = x/20 = 700/20 = 35 

Second car: 
Gallons = (1300 - x)/15 = (1300 - 700)/15 = 600/15 = 40