A = 1/3 + 5/4 = 4/12 + 15/12 = 19/12
B = 3/7 - 10/21 = 9/21 - 10/21 = 1/21
C = (15*7*1)/(28*25*6) = 105/4200
E = 5/4 - 3/2 + 7/6 = 15/12 - 18/12 + 14/12 = 11/12
F = 2 + (7*1)/(9*2) = 2 + 7/18 = 36/18 + 7/18 = 43/18
H = 3/4 - (2*1)/(7*2) = 3/4 - 2/14 = 21/28 - 4/28 = 17/28