We have numbers 4526 and 6639. Let's start adding them together.

Step 1: We'll start by adding the digits 6 & 9 in column 1 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 2 & 3 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 4 & 6 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 4526 + 6639 = 11165.

