Answer:
8.33 gallons
Step-by-step explanation:
Given: A car's fuel economy is 30 mpg. a warning light is displayed if the remaining distance that can be driven before the car runs out of gas drops below 50 miles.
To Find: initially the car has 10 gallons of gas. how many gallons, g, can be used before the warning light comes on.
Solution: 
Total fuel in car

fuel economy of car 

fuel required to ride 30 mile 

fuel required to ride 1 mile 

Now,
Fuel required to ride 50 miles 

fuel left in car when warning light is displayed 

 

Amount of fuel that can be consumed before warning light dislays
 

 

 
 
 

8.33 gallons fuel can be used before warning light comes on