(3/4-2/3)÷1/5=1/12ch35=5/124/5×7/8+7/8÷5 =(4/5+1/50×7/8=1×7/8=7/8(1-8/15×3/4)÷3/5 =(1-2/5)×5/3=3/5×5/3=1(3/8+2/17)×8+1/17=3/8×8+(16/17+1/17)=3+1=4