OK, let's do this. We've got 7017 and 2906 and we're adding them all together.

Step 1: We'll start by adding the digits 7 & 6 in column 1 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

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

Step 3: We'll start by adding the digits 0 & 9 in column 3 and get 9.

Step 4: We'll start by adding the digits 7 & 2 in column 4 and get 9.

So, 7017 + 2906 = 9923.

