15-2(7/9)-3(2/9)
= 15 -2 - 3 - (7/9) -(2/9)
= 15 -2 -3 - (7/9+2/9)
= 15 -2 -3 -1
= 9这是五年级的题目哦这是简便方法啊不然就都通分，那计算量就大了