To find out how much wall area could be covered with 15 gallons of paint, we first need to determine the area that can be covered by 1 gallon of paint.
According to the problem, 5 gallons of paint cover 750 square feet. We can calculate the coverage per gallon:
Now, we can find out how much area can be covered by 15 gallons of paint:
Therefore, 15 gallons of paint can cover 2250 square feet of wall area.