We have numbers 2635 and 6021. Let's start adding them together.

Step 1: We'll start by adding the digits 5 & 1 in column 1 and get 6.

Step 2: We'll start by adding the digits 3 & 2 in column 2 and get 5.

Step 3: We'll start by adding the digits 6 & 0 in column 3 and get 6.

Step 4: We'll start by adding the digits 2 & 6 in column 4 and get 8.

So, 2635 + 6021 = 8656.

