To add, first find a common denominator which is 300.

Convert each fraction:
3/20 = 45/300
7/30 = 21/300
9/50 = 27/300

Adding them together:
45/300 + 21/300 + 27/300 = 93/300

Therefore, 3/20 + 7/30 + 9/50 = 93/300 or simplified, 31/100.

To add:
7/4 = 105/60
11/70 = 6/60
13/30 = 26/60

Adding them together:
105/60 + 6/60 + 26/60 = 137/60

Therefore, 7/4 + 11/70 + 13/30 = 137/60 or simplified, 137/60.