(5/12-3/5)-(7/12-2/5)
=5/12-3/5-7/12+2/5
=5/12-7/12-(3/5-2/5)
=-1/6-1/5
=-11/30
不能不是负数,因为算出来结果是负数哦
请检查数据是否被抄错