OK, let's do this. We've got 7780 and 8403 and we're adding them all together.

Step 1: We'll start by adding the digits 0 & 3 in column 1 and get 3.

Step 2: We'll start by adding the digits 8 & 0 in column 2 and get 8.

Step 3: We'll start by adding the digits 7 & 4 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 7 & 8 in column 4 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

So, 7780 + 8403 = 16183.

