Please show me the solution for: Troy bakes 2 pans of brownies, cut into 16 pieces per pan.  The guests eat all of 1 pan, and 75% of the 2nd pan.  One tub of ice cream provides 8 scoops.  If all but 4 of the guests eat the brownies ala mode (with 2 scoops of vanilla ice cream), how many tubs of ice cream did the guests eat?