72/126 - 49/126 = 23/126
13 - 14 - 18 - 23 - 32 = -74
4 - 18 = -14
32-14=18
4 and 17/18
-60
27
18-(-16) = 34
-7/9 - 5/10 = -7/9 - 1/2 = -14/18 - 9/18 = -23/18
You have to get the same common denominator, 9x2 is 18, so 7x2 is 14. 14/18-5/18 is 9/18. 9/9 is 1 and 18/9 is 2, so you are left with 1/2
18/27 minus 44/81 is 10/81
12/14, 18/21
6/7 - 2/3 = 18/21 - 14/21 = 4/21