To find the sum of two numbers, we must add them together. However, in this case we are adding a negative number. Addition of a negative number can also be written as subtraction, and this method is easier for most people to compute and understand, so we are going to rewrite the expression as follows:
The volume of a crate is b x l x h. Reverse it to get 3 times 6 times h = 72. 3 times 6 is 18, so you know 18h=72. Divide both sides by 18 to get h = 4 ft.
