甲乙两商店中某种商品的定价相同。甲商店按定价销售这种商品，销售额是7200元；乙商店按定价的八折销售，比甲商店多售出15件，销售额与甲商店相同。则甲商店售出多少件这种商品？

数学题解答：一、用算术解是：7200×（1-80%）=1440（元） 乙商店的单价：1440÷15=96（元） 定价：96÷80%=120（元） 7200÷120=60（件）

二、用方程解（由：gzbzluojie提供手写解题方案）

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