Okay, we are given 5109 and 9910. Let's add them up step by step.

Step 1: We'll start by adding the digits 9 & 0 in column 1 and get 9.

Step 2: We'll start by adding the digits 0 & 1 in column 2 and get 1.

Step 3: We'll start by adding the digits 1 & 9 in column 3 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 5 & 9 in column 4 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 5109 + 9910 = 15019.

