First, you should add 7.75+7.05= 14.8 1.15x2 since there were <u>2</u> glasses. 1.15x2=2.3 14.8+2.3= 17.1 since he gave the waiter $20.00 to pay for it, you do $20.00-17.1= 2.9
So we have a 6 at the bottom, and the root is 3, so hmm how to take it out, simple enough, just let's get something to make the 6 a 6³, so it comes out of the root