Including the bus driver, there are 15 people on a bus. during the bus ride, each person produces 750 btus (british thermal units). the interior of the bus measures 38 feet by 8.5 feet by 6.25 feet. how many btus per cubic foot are produced?

This is the concept of applications of volume. We are required to calculate BTUs per cubic foot. This will be given by the formula:
(BTU)/volume
Total BTU=15*750=11,250
(assuming the bus is a perfect cuboid) volume of the bus will be;
volume=length*width*height
=38*8.5*6.25
=2018.75 ft^2
Thus the BTUs per foot will be:
11250/2018.75
5.57 BTUs/ft

The decimal expansion would be .27 repeated