1/2+3/4-3/10=5/4-3/10=19/20 2/3-4/7+5/6=2/3+5/6-4/7=3/2-4/7=13/14 10/(2/3+1/2)=10÷7/6=60/7=8又4/7 1/6-(5/12-1/4)=1/6-1/6=0