a) 1/5 + 3/5 = (1+3)/5 = 4/5
b) -5/9 + 1/9 = (-5+1)/9 = -4/9
c) 4/11 - 7/11 = (4-7)/11 = -3/11
d) 7/4 - 1/4 = (7-1)/4 = 6/4 = 3/2
e) 4/7 + 3/4 + 2/7 + 5/4 + 1/7 = (16/28) + (21/28) + (8/28) + (35/28) + (4/28) = 84/28 = 3
f) 7/5 + 4/20 = (28/20) + (1/5) = 7/5 + 4/20 = 7/5 + 1/5 = 8/5
g) 4/9 - 2/3 = (4/9) - (6/9) = -2/9
h) 5/6 - 7/18 = (15/18) - (7/18) = 8/18 = 4/9
i) 7/6 + 9/8 = (28/24) + (27/24) = 55/24
j) -7/12 + 7/9 = (-7/12) + (28/36) = -7/12 + 7/12 = 0