Answer:
The number of gallons consumed by the first car were 30
The number of gallons consumed by the second car were 20
Explanation:
Let
x -----> number of gallons consumed by the first car during one week
y -----> number of gallons consumed by the second car during one week
we know that
The efficiency multiplied by the number of gallons is equal to miles
30x+40y=1,700 -----> equation A
x+y=50 ----> equation B
Solve the system by graphing
Remember that the solution is the intersection point both graphs
The solution is the point (30,20)
see the attached figure
therefore
The number of gallons consumed by the first car were 30
The number of gallons consumed by the second car were 20