=7/12÷1/24+3/8÷1/24-5/6÷1/24=14+9-20=3(除以一个数等于乘以这个数的倒数)
（7/12+3/8-5/6）÷1/24=(3/8-3/12)÷1/24=3/24÷1/24=3
