OK, let's do this. We've got 3588 and 4007 and we're adding them all together.

Step 1: We'll start by adding the digits 8 & 7 in column 1 and get 15.
We'll write down the last digit 5 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 5 & 0 in column 3 and get 5.

Step 4: We'll start by adding the digits 3 & 4 in column 4 and get 7.

So, 3588 + 4007 = 7595.

