12分之5＋8分之7减6分之5 5/12 + 7/8 - 5/6= 10/24 + 21/24 - 20/24= (10+21-20)/24= 11/24
5/12+7/8-5/6=10/24+21/24-20/24=31/24-20/24=11/24
