17
12 + 1.25 t
The equation to describe this will be
y
=
1
2
+
1
.
2
5
t
y=12+1.25t, where y is the number of gallons which would be in the tank, and t is the number of hours.
When t = 4,
y
=
1
7
y=17 gallons.
So, the gas left in the tank after driving for 4 hours is 17 gallons
The gas left in the tank after driving for t hours is 12 + 1.25 t gallons.