OK, let's do this. We've got 723 and 140 and we're adding them all together.

Step 1: We'll start by adding the digits 3 & 0 in column 1 and get 3.

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

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

So, 723 + 140 = 863.

