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1      1        3      2        5
--  + ---- = ---- +----- = ------
2      3        6       6         6


1/4 + 2/5= 5/20 +8/20= 13/20


2/3+1/4= 8/12+ 3/12= 11/12

3/4+2/5= 15/20+8/20=23/20= 1 3/20

5/7- 1/6= 30/42-7/42=23/42
3/4-1/3=9/12-4/12=5/12
1/8+1/4= 1/8+ 2/8= 3/8
2/3-5/9= 6/9-5/9 =1/9
1/2-5/12= 6/12-5/12=1/12
5/12-2/9=15/36-8/36=7/36
1/8+7/12=  3/24+14/24=17/24
3/4-1/6= 9/12-2/12=7/12
5/9+3/4= 20/36+27/36=47/36= 1 11/36
23/40-3/8=23/40-15/40=8/40
9/35-3/28= 36/140-15/140=21/140

1)5/6
2)13/20
3)11/12
4)1   3/20