1. 3/4-3/4÷3+9/25
=3/4-3/4×1/3+9/25
= 3/4-1/4 +9/25
=1/2+9/25
=25/50+18/50
=43/50
2. 2/3÷1/2-5/3×2/5
= 2/3×2-2/3
= 2/3×（2-1）
= 2/3
3. 2÷[(1+2/5)×3/7]
= 2÷(7/5×3/7)
= 2÷3/5
= 2×5/3
=10/3
4. 5/8×3/4+1/4×5/8+5/8
= 5/8 ×(3/4+ 1/4+1)
= 5/8 ×2
=5/4
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