For each alphabet, you're giving it a value. So, since A is the first letter of the alphabet, its value would be 1. Since B is the second letter of the alphabet, its value would be 2, and so on.
What you have to do for A is to find the total number by adding each value from your name. In example, if your name was Bob, it would be 19 (2 + 15 + 2)
For B you just have to write two 3-letter words that would make up 20. An example can be DIG (4 + 9 + 7 = 20)