计算下面各题,能简算的要简算1/2+4/7+3/7 =1/2+(4/7+3/7)=1/2+1=1又1/21/10+3/8-2/5 =19/40-2/5=3/401-(2/3+1/8) =1-2/3-1/8=1/3-1/8=5/247/8-(2/3-1/4) =7/8+1/4-2/3=9/8-2/3=11/241/9+(1/6+2/9)+5/6=(1/9+2/9)+(1/6+5/6)=1/3+1=1又1/3