13/15-(5/7-3/5)=79/105 17/18+(1/2-1/3)=10/9
13/15 - (5/7 - 3/5) = 91/105 - 75/105 + 63/105 = 79/105
17/18 + (1/2 - 1/3) = 17/18 + 1/6 = 17/18 + 3/18 = 20/18 = 10/9
1、=一百零五分之七十九
2、=一又九分之一
所有分母通分后得出
第一个等于79/105
第二个等于10/9
13/15-(5/7-3/5)=79/105
17/18+(1/2-1/3)=10/9