5/6－5/9×7/10＝喊碰5/6－7/18＝举扮15/18－7/18＝4/正渗灶9
5/6-5/9×7/10=5×(1/6-7/90)=5×(15/90-7/90)=5×8/桥源90=5×4/敏丛态郑蔽45=4/9
