Let
x ----> gallons consumed by the first car
y ----> gallons consumed by the second car
so
we have the system of equations
x+y=35 ------> x=35-y ------> equation 1
35x+30y=1,125 -----> equation 2
Solve the system
substitute equation 1 in equation 2
35(35-y)+30y=1,125
solve for y
1,225-35y+30y=1,125
35y-30y=1,225-1,125
5y=100
y=20
Find out the value of x
x=35-20=15
therefore
The answer is
First car 15 gallons
second car 20 gallons
