脱式计算，能简算的要简算 7/12+（7/8-3/4） 16/25-（14/19-9/25

7/12+(7/8-6/8)=7/12+1/8=14/24+3/24=17/24
16/25-（14/19-9/25）=16/25+9/25-14/19=1-14/19=5/19
4/5-4/7+1/2=28/35-20/35+1/2=8/35+1/2=16/70+35/70=51/70
7/10-1/4+3/10-3/4 2- 3/5+1/4
=7/10+3/10-3/4 2- 3/5
=1-3/4 2- 3/5
=39/42-3/5
=195/210-126/210
=69/210
=23/70

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7/12+（7/8-3/4）
=7/12 + 1/8
=14/24 + 3/24
= 17/24

16/25-（14/19-9/25）
=16/25 + 9/25 - 14/19
= 1 - 14/19
= 5/19

4/5-4/7+1/2
= 28/35 - 20/35 +1/2
= 8/35+ 1/2
= 16/70 +35/70
= 51/70

7/10-1/4+3/10-3/4
=(7/10 + 3/10)-(1/4 + 3/4)
= 1 - 1
= 0

2- 3/5+1/4
= 10/5 - 3/5 + 1/4
= 7/5 + 1/4
= 28/20 + 5/20
= 33/20

等于一又1/24。