1/6×(5-2/3) =1/6×(4+1-2/3) =1/6×(4+1/3) =4/6+1/18 =12/18+1/18 =13/18 其实不用简算 直接计算就可以 1/6×(15/3-2/3) =1/6×13/3 =13/18