3/7×4/5+4/7×2/5
=6/7×2/5+4/7×2/5
=（6/7+4/7)×2/5
=10/7×2/5
=4/7.3/4×1/17+1/4×14/17简便3/4×1/17+1/4×14/17=1/4×3/17+1/4×14/17=（1/4）×(3/17+4/17)=(1/4)×1=1/4.再打一遍3/4×1/17+1/4×14/17=1/4×3/17+1/4×14/17=（1/4）×(3/17+14/17)=(1/4)×1=1/4.3/4×5/7×4/3-1/7还有1又1/12+1/4×7/6-11/8还有1又1/12+1/4×7/6-11/8简便