Here we go! We're going to add 3423 and 4449 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 & 4 in column 2 and get 7.

Step 3: We'll start by adding the digits 4 & 4 in column 3 and get 8.

Step 4: We'll start by adding the digits 3 & 4 in column 4 and get 7.

So, 3423 + 4449 = 7872.

