Xiaoming and Xiaojun went to buy greeting cards. Xiaojun bought 2.5 times as many as Xiaoming. After Xiaoming bought another 15 cards, the two bought the same number of cards. How much did each buy Why use 2.5-1?

Xiaoming and Xiaojun went to buy greeting cards. Xiaojun bought 2.5 times as many as Xiaoming. After Xiaoming bought another 15 cards, the two bought the same number of cards. How much did each buy Why use 2.5-1?

Xiaoming = 15 (2.5-1) = 10 sheets
Xiaojun = 10 * 2.5 = 25 sheets