If 18 inches is equal to 1
First, you can figure out the relationship between 18 and 36, then 18 and 72, then 18 and 144. With this information, it will be easier to solve for number of feet. Or, you can find the number of inches in one foot first.
36 is 2 times 18. To find how many feet 36 inches is, you would need to multiple 1.5 by 2, since 1.5 is equal to 18 inches. Use this information to help you with the rest of the problem.