1.3/4x(2/5-1/3)+7/8÷1/2
=3/4x2/5-3/4x1/3+7/8x2/1
=3/10-1/4+7/4
=0.3+3/2=1.8
2. 3.2x4/5x7/8
=3.2x7/10
=3.2x0.7=2.24
3. 3.5-2/3+3/5
=3.5-10/15+9/15
=35/10+1/15
=105/30+2/30
=107/30=3又17/30
一
3/4×（2/5-1/3）+7/8÷1/2=3/4×（6/15-5/15）+7/4=1/20+4/7=7/140+80/140=87/140
二
3.2×4/5×7/8=3.2×28/40=3.2×0.7=2.24
三
3.5-2/3+3/5=3.5-10/15+9/15=3.5-1/15=105/30-2/30=103/30
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