OK, let's do this. We've got 3629 and 5122 and we're adding them all together.

Step 1: We'll start by adding the digits 9 & 2 in column 1 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

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

Step 3: We'll start by adding the digits 6 & 1 in column 3 and get 7.

Step 4: We'll start by adding the digits 3 & 5 in column 4 and get 8.

So, 3629 + 5122 = 8751.

