Let's solve this addition problem. We have 4334 and 2155, and we need to add them together.

Step 1: We'll start by adding the digits 4 & 5 in column 1 and get 9.

Step 2: We'll start by adding the digits 3 & 5 in column 2 and get 8.

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

Step 4: We'll start by adding the digits 4 & 2 in column 4 and get 6.

So, 4334 + 2155 = 6489.

