Not to worry, we've got 312 and 105. Let's get to adding them!

Step 1: We'll start by adding the digits 2 & 5 in column 1 and get 7.

Step 2: We'll start by adding the digits 1 & 0 in column 2 and get 1.

Step 3: We'll start by adding the digits 3 & 1 in column 3 and get 4.

So, 312 + 105 = 417.

