For $1.80 a grocer buys a case of fruit which contains 12 dozen. He knows that 2 dozen will spoil before he sells them. At what price per dozen must he sell the good ones to gain 1/3 of the whole cost?
I assume you mean she wants to make 50% profit, based on a cost of $1.80/dozen. (The wording is ambiguous. If the problem was presented as you posted it, it's from a pretty sloppy text.)