424.
1) 2/45 + 7/9 = 2/45 + 35/45 = 37/45
2) 2/5 + 4/25 = 10/25 + 4/25 = 14/25
3) 1/6 + 7/18 = 3/18 + 7/18 = 10/18 = 5/9
4) 19/42 + 6/7 = 19/42 + 36/42 = 55/42 = 1 13/42
5) 3/32 + 5/8 = 3/32 + 20/32 = 23/32
6) 3/8 + 1/56 = 21/56 + 1/56 = 22/56 = 11/28
425.
1) 1/3 - 1/9 = 3/9 - 1/9 = 2/9
2) 10/21 - 1/3 = 10/21 - 7/21 = 3/21 = 1/7
3) 14/15 - 3/5 = 14/15 - 9/15 = 5/15 = 1/3
4) 17/18 - 1/9 = 17/18 - 2/18 = 15/18 = 5/6
5) 4/9 - 13/45 = 20/45 - 13/45 = 7/45
6) 1/3 - 7/30 = 10/30 - 7/30 = 3/30 = 1/10