Answer: the fuel efficiency of the first car is 20 miles per gallon.
the fuel efficiency of the second car is 15 miles per gallon.
Step-by-step explanation:
Let x represent the number of miles per gallon of the first car.
Let y represent the number of miles per gallon of the second car.
During one particular week, the first car consumed 20 gallons of gas and the second consumed 15 gallons of gas. The two cars drove a combined total of 625 miles. It means that
20x + 15y = 625- - - - - - - - - - 1
The sum of their fuel efficiencies was 35 miles per gallon. It means that
x + y = 35
Substituting x = 35 - y into equation 1, it becomes
20(35 - y) + 15y = 625
700 - 20y + 15y = 625
- 20y + 15y = 625 - 700
- 5y = - 75
y = - 75/ - 5
y = 15
x = 35 - y = 35 - 15
x = 20
