5 + 2 3/8 = (5 + 2) + 3/8 = 7 3/8 = (7*8+3)/8 = 59/8
10 3/4 - 7 = 3 3/4 = 15/4
4 1/6 + 10 = 14 1/6 = 85/6
12 8/15 - 12 = 8/15
4 1/9 + 3 4/9 = (4 + 3) + (1/9 + 4/9) = 7 5/9 = 68/9
7 5/7 - 4 3/7 = (7 - 4) + (5/7 - 3/7) = 3 2/7 = 23/7
3 8/11 + 5 2/11 = (3 + 5) + (8/11 + 2/11) = 8 10/11 = 98/11
9 7/12 - 7 6/12 = (9 - 7) + (7/12 - 6/12) = 2 1/12 = 25/12
4 3/5 + 2 4/5 = (4 + 2) + (3/5 + 4/5) = 6 7/5 = 6 + 5/5 + 2/5 = 7 2/5 = 37/5
8 9/13 + 7 12/13 = 17 + 21/13 = 18 8/13 = 242/13
5 3/5 - 1 4/5 = (5-1) + (3/5-4/5) = 3 + (5/5+3/5-4/5) = 3 4/5 = 19/5
4 5/11 - 2 8/11 = (4-2) + (5/11-8/11) = 1 + (11/11+5/11-8/11) = 1 8/11 = 19/11
4 - 5/9 = 3 + 9/9 - 5/9 = 3 4/9 = 31/9
8 - 7/12 = 7 + 12/12 - 7/12 = 7 5/12 = 89/12
5 - 3 3/8 = (5 - 3) - 3/8 = 1 + 8/8 - 3/8 = 1 5/8 = 13/8
4 - 3 5/9 = (4 - 3) - 5/9 = 1 - 5/9 = 9/9 - 5/9 = 4/9
Я на всякий случай еще перевел все смешанные дроби в неправильные.
Если это не нужно - можете не писать, но с неправильными дробями обращаться легче, чем со смешанными.