OK, let's do this. We've got 2250 and 9940 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 5 & 4 in column 2 and get 9.

Step 3: We'll start by adding the digits 2 & 9 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 2 & 9 in column 4 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 2250 + 9940 = 12190.

