（1又3/4-7/8-7/12)÷﹙－7/8﹚＋﹙－7/8﹚÷﹙1又3/4－7/8－7/12﹚=(24*（7/4-7/8-7/12))÷(24*﹙－7/8﹚)＋(24*﹙－7/8﹚)÷(24*﹙7/4－7/8－7/12﹚)=(42-21-14)÷(-21)＋(-21)÷(42-21-14)=-1/3 -3=-3又1/3
