Nathan B. answered 04/07/15
Tutor
5
(20)
Elementary and Algebraic skilled
Think of it this way. You start off with 15/15 customers available. 5/15 got green tea. 2/15 got jasmine. 5/15 got herbal. what part of the customers did NOT purchase any of those teas listed?
Since it's asking what is left, we need to remove the others who ordered gree, jasmine, and herbal from our count. And when we remove them, what operation do we need to use?