Answer:
36 bottles
Explanation:
You want to know the number of bottles that must be painted and sold in order to make a profit of $120, given that 3 bottles can be purchased for $11, and each bottle can be sold for $7.
Profit
The profit on each bottle is the difference between its cost and what it is sold for. The cost of 1 bottle is 1/3 of the cost of 3 bottles.
profit = selling price - purchase price
profit = $7/bottle - ($11/(3 bottles)) = $(21/3 -11/3)/bottle = $(10/3)/bottle
Bottles
To make a profit of $120, you need n bottles such that ...
(10/3)n = 120
n = 36 . . . . . . . . . multiply by 3/10
The club needs to buy, paint, and sell 36 bottles to raise $120.