step 1
Find the number of miles run by each bus in one day
we know that
speed=distance/time
distance=speed*time
distance=(15 mi/h)*3 h=45 miles
Find the number of miles run by the total buses in one day
Multiply by 300
300*45=13,500 miles
Find the number of miles run by the total buses in 22 days
13,500*22=297,000 miles
step 2
Find the number of gallons to run 297,000 miles
we know that
the fuel economy of the buses is 10 mi/gal
so
by proportion

step 3
Find the cost of 29,700 gal of gasoline
we know that
the gasoline costs $4.10 per gallon
then
29,700*4.10=$121,770
therefore
the answer is
the cost of the gasoline is $121,770