(1) The two boxes of eggs bought by customer B are not cost-effective.

Customer B bought two boxes of 60 eggs (30×2) and spent 24 yuan (12×2). According to the original price, 24 yuan can buy about 5 1(24÷( 14/30)). Now she bought 60 eggs, 20 of which were broken, but in fact she got 40.

(2) If customer A buys X eggs, the money spent now is 12X/30 yuan, whereas it used to cost 14X/30 yuan to buy the same number of eggs. According to the meaning, the equation is:12x/30 = 2x14x/30-96.

The solution is x = 180.

In order not to waste, it must be eaten within the shelf life of 18 days. So at least 180 ÷ 18 = 10 pieces are consumed every day.