1、0.2+1/5×3/7+4/7×20%
=0.2×(1+3/7+4/7)
=0.2×2
=0.4
2、[1-(1/4+3/8)]÷1/3
=[1-5/8]÷1/3
=3/8÷1/3
=9/8
3、5/9×3/8+4/9×0.375
=5/9×3/8+4/9×3/8
=3/8×(5/9+4/9)
=3/8
4、1/50+(1-2/5)÷3/20
=1/50+3/5÷3/20
=1/50+4
=4又1/50你说的是什么啊，根本不是这些题目，你复制粘贴的吧