To solve these equations, you need to find a common denominator for each set of fractions and then perform the operations.

1) 3/4 + 4/5 + 1/20:

Finding a common denominator: The least common multiple of 4, 5, and 20 is 20.

Rewriting the fractions with the common denominator:

3/4 = 15/20
4/5 = 16/20
1/20 = 1/20

Adding the fractions:

15/20 + 16/20 + 1/20 = 32/20 = 8/5

So, 3/4 + 4/5 + 1/20 = 8/5.

2) 3/4 + 5/12 - 1/9:

Finding a common denominator: The least common multiple of 4, 12, and 9 is 36.

Rewriting the fractions with the common denominator:

3/4 = 27/36
5/12 = 15/36
1/9 = 4/36

Performing the operations:

27/36 + 15/36 - 4/36 = 38/36 = 19/18

So, 3/4 + 5/12 - 1/9 = 19/18.