OK, let's do this. We've got 212 and 663 and we're adding them all together.

Step 1: We'll start by adding the digits 2 & 3 in column 1 and get 5.

Step 2: We'll start by adding the digits 1 & 6 in column 2 and get 7.

Step 3: We'll start by adding the digits 2 & 6 in column 3 and get 8.

So, 212 + 663 = 875.

