i need the answer soon

Question

A family has two cars. The first car has a fuel efficiency of 15

 miles per gallon of gas and the second has a fuel efficiency of 35

 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 60

 gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

35X + 15(60-X) = 1700

35X-15X = 1700-900

20X = 800

X = 800/20 = 40 gallons for the 35mph car

60-X = 60-40 = 20 gallons for the 15mph car

Answer 2

Let x be the gallons consumed by the first car and y the gallons consumed by the second car.

From the description

x + y = 60 gallons total used by both cars --> y = 60-x

15x + 35y = 1700

15x + 35(60-x) = 1700

15x + 2100-35x = 1700

20x = 400

x = 20

y = 60-20 = 40.

The first car consumed 20 gallons and the second car consumed 40 gallons.

Answer 3

Let x = number of gallons used by the first car and y = number of gallons used by the second car

15x + 35y = 1700

x + y = 60

From the second equation, y = 60 - x.

So, 15x + 35(60 - x) = 1700

-20x = -400

x = 20 gal and y = 40 gal