OK, let's do this. We've got 4123 and 4709 and we're adding them all together.

Step 1: We'll start by adding the digits 3 & 9 in column 1 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 2 & 0 in column 2 and get 3.

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

Step 4: We'll start by adding the digits 4 & 4 in column 4 and get 8.

So, 4123 + 4709 = 8832.

