5/12÷【（5/9-1/6）÷7/3】 =5/12÷【5/9x3/7-1/6x3/7】 =5/12÷（5/21-1/14） =5/12÷（10/42-3/42） =5/12÷7/42 =5/12÷1/6 =5/12x6 =5/2 =2.5 您的采纳是我答题的动力,