OK, let's do this. We've got 2724 and 7235 and we're adding them all together.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 2 & 3 in column 2 and get 5.

Step 3: We'll start by adding the digits 7 & 2 in column 3 and get 9.

Step 4: We'll start by adding the digits 2 & 7 in column 4 and get 9.

So, 2724 + 7235 = 9959.

