OK, let's do this. We've got 9509 and 379 and we're adding them all together.

Step 1: We'll start by adding the digits 9 & 9 in column 1 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 0 & 7 in column 2 and get 8.

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

Step 4: We'll start by adding the digits 9 & 0 in column 4 and get 9.

So, 9509 + 379 = 9888.

