Xiaodong and Xiaoliang went to the canteen to buy composition books, Xiaodong bought 5 copies, Xiaoliang bought 8 copies, each composition was c yuan, how much more did Xiaoliang pay than Xiaodong.
小冬和小亮去小卖部买作文本，小冬买了5本，小亮买了8本，每本作文本c元，小亮比小冬多付多少元．
<result>3</result>