Question

The Olivares family forgot to fill up the gasoline tank of their minivan at the beginning of a long trip. After driving 120 miles, there were 10 gallons remaining in the tank.

If their car used fuel at the rate of 1 gallon every 20 miles, which equation describes the number of gallons, y, remaining in the tank after x miles?

Answer 1

the van uses 1 gal/20 mi
so amount used = x/20
the tank holds V gallons
so amount remaining after x miles
y = V - x/20
we are given a point on that line
10 = V - 120/20
V = 10 + 6 = 16 gallons
so in the end
y = 16 - x/20