Given :
Shawn's family car holds 16 gallons of fuel.
Each day the car uses 0.8 gallons to get to school and back.
A warning light comes on when there is less than 1.5 gallons left in the fuel tank.
To Find :
How many days can Shawn drive the car before the warning lights come on.
Solution :
Let, after x days warning come.
So,

Therefore, at 19th day the warning light will start glowing.
Hence, this is the required solution.