Hello, mathdumby!

I had to baby-talk my way through this . . .A car averages 8.5 L/100km in city driving and 6.3 L/100km on the highway.

In 720 km of driving , it used 55.7 L of fuel.

a) How far was the car driven in the city?

b) How much fuel did it use in city driving?

i figured that i would let the distance driven in the city be km,

and the distance driven in the highway be km

The first equation, in my opinion, should be: . . . . . Right!

In the city, the car uses 8.5 liters for 100 km of driving.

. . That is: . liters per kilometer.

For km, it used: . liters of fuel.

On the highway, the car uses 6.3 liters for 100 km of driving.

. . That is: . liters per kilometer.

For km, it used: . liters of fuel.

It used a total of 55.7 liters of fuel: . . . . . There!

(I got: . )