Need help with math, pls help, im alone and scared.

Question

A family has two cars. During one particular week, the first car consumed 35 gallons of gas and the second consumed 15 gallons of gas. The two cars drove a combined total of 1275 miles, and the sum of their fuel efficiencies was 45 miles per gallon. What were the fuel efficiencies of each of the cars that week?

Answer 1

x+y = 45

35x +15y = 1275

multiply 1st equation by 15

15x +15y = 15(45) = 675

subtract last equation from 2nd equation

20x = 600

x = 600/20 = 30 mpg = gas mileage of 1st car

y =45-30 = 15 mph = gas mileage of 2nd car

35(30)+15(15) = 1050+225 = 1275