To add fractions, we need to find a common denominator:

7/12 + 7/20
Common denominator: 60
Rewrite fractions with denominator 60:
28/60 + 21/60
Combine the numerators:
(28 + 21)/60 = 49/60

3/8 + 1/18
Common denominator: 72
Rewrite fractions with denominator 72:
27/72 + 4/72
Combine the numerators:
(27 + 4)/72 = 31/72

1/12 + 11/14
Common denominator: 84
Rewrite fractions with denominator 84:
7/84 + 66/84
Combine the numerators:
(7 + 66)/84 = 73/84

2/15 + 7/12
Common denominator: 60
Rewrite fractions with denominator 60:
8/60 + 35/60
Combine the numerators:
(8 + 35)/60 = 43/60

Subtracting fractions:

9/14 - 5/12
Common denominator: 84
Rewrite fractions with denominator 84:
54/84 - 35/84
Subtract the numerators:
(54 - 35)/84 = 19/84

Adding fractions:

19/75 + 7/50
Common denominator: 150
Rewrite fractions with denominator 150:
38/150 + 21/150
Combine the numerators:
(38 + 21)/150 = 59/150

Therefore, the solutions are:

49/6031/7273/8443/6019/8459/150