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

35x + 15(45-x) = 1275

35x -15x = 1275-15(45)

20x = 1275-675 = 600

x = 600/20 = 30 miles per gallon

45-x = 15 miles per gallon

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