OK, let's do this. We've got 8860 and 2520 and we're adding them all together.

Step 1: We'll start by adding the digits 0 & 0 in column 1 and get 0.

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

Step 3: We'll start by adding the digits 8 & 5 in column 3 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 8 & 2 in column 4 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

So, 8860 + 2520 = 11380.

