fuel efficiency word problem help needed

Question

A family has two cars. The first car had 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 week, the two cars went a combined total of 1550 miles,for a total gas consumption of 55 gallons. How many gallons were consumed by each of the two cars that week?

Answer 1

two unknowns so for solution need two independent equations

x+y=55

20x+35y=1550

first equation same as 20x+20y=1100

subtracting like terms

0x+15y=450

y=30 gallons,,,x=25 gallons