(200-x)÷6=12.5两边同时乘以6：200-x=75两边同时减去200：-x=-125两边同时乘以-1：x=125
(200-x)÷6＝12.5200-x=12.5X6x=200-75x=125
解:200-x=12.5×6200-x=75x+75=200x=200-75x=125
