OK, let's do this. We've got 621 and 174 and we're adding them all together.

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

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

Step 3: We'll start by adding the digits 6 & 1 in column 3 and get 7.

So, 621 + 174 = 795.

