Alright, let's solve this problem step by step. We have 6525 and 9644 and we're adding them together.

Step 1: We'll start by adding the digits 5 & 4 in column 1 and get 9.

Step 2: We'll start by adding the digits 2 & 4 in column 2 and get 6.

Step 3: We'll start by adding the digits 5 & 6 in column 3 and get 11.
We'll write down the last digit 1 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, 6525 + 9644 = 16169.

