能简算的要简算 1、2/3×5/7+2/3×2/7

2/3×5/7+2/3×2/7
= 2/3×(5/7+2/7)
= 2/3
2、7/2×3/7÷6
= 3/2 x 1/6
= 1/4
3、8×5/6+2/5÷4
= 4 x 5/3 + 1/5 x 1/2
= 20 /3 + 1/10
= (200+ 3 ) /30
= 203 /30
4、（1/2+2/5）÷3/2
= (5+4 ) /10 x 2/3
= 9/10 x 2/3
= 3 / 5
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