3/8×(7/8+1/6)÷3/4=3/8×(1/8+1/6)×4/3=1/2×(1/8+1/6)=1/2×(3/24+4/24)=1/2×7/24=7/489/10×(5/6-2/5)÷13/25=9/10×(25/30-12/30)=9/10×13/30×25/13=9/10×25/30=9/10×5/6=3/41＋3又1/6+5又1/12+7又1/20+9...