OK, let's do this. We've got 2707 and 4121 and we're adding them all together.

Step 1: We'll start by adding the digits 7 & 1 in column 1 and get 8.

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

Step 3: We'll start by adding the digits 7 & 1 in column 3 and get 8.

Step 4: We'll start by adding the digits 2 & 4 in column 4 and get 6.

So, 2707 + 4121 = 6828.

