OK, let's do this. We've got 387 and 7605 and we're adding them all together.

Step 1: We'll start by adding the digits 7 & 5 in column 1 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 8 & 0 in column 2 and get 9.

Step 3: We'll start by adding the digits 3 & 6 in column 3 and get 9.

Step 4: We'll start by adding the digits 0 & 7 in column 4 and get 7.

So, 387 + 7605 = 7992.

