We've got two numbers: 6431 and 9634. Let's find their sum.

Step 1: We'll start by adding the digits 1 & 4 in column 1 and get 5.

Step 2: We'll start by adding the digits 3 & 3 in column 2 and get 6.

Step 3: We'll start by adding the digits 4 & 6 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 6 & 9 in column 4 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

So, 6431 + 9634 = 16065.

