Let the number of hours = h
Multiply the rate per hour by hours and add to the rental fee.
This at most can equal the amount you have.
Equation: 6h+ 13.50 <= 37.50
Solve for h:
6h + 13.50 <= 37.50
Subtract 13.50 from both sides:
6h <= 24.00
Divide both sides by 6:
H <= 4
You can rent the canoe for 4 hours maximum.