a) 11 / 12 - 1 / 6 = 11/12 - 2/12 = 9/12 = 3/4
b) 5 / 36 - 1 / 9 = 5/36 - 4/36 = 1/36
c) 19 / 20 - 4 / 5 = 19/20 - 16/20 = 3/20
d) 5 / 7 - 3 / 14 = 10/14 - 3/14 = 7/14 = 1/2
e) 20 / 63 - 2 / 9 = 20/63 - 14/63 =6/63 = 2/31
f) 11 / 24 - 5 / 12 = 11/24 - 10/24 = 1/24
g) 5 / 18 - 1 / 6 =5/18 - 3/18 = 2/18 = 1/9
h) 1 / 4 - 3 / 7 = 7/28 - 12/28 = - 5/28