Okay, we are given 4263 and 6003. Let's add them up step by step.

Step 1: We'll start by adding the digits 3 & 3 in column 1 and get 6.

Step 2: We'll start by adding the digits 6 & 0 in column 2 and get 6.

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

Step 4: We'll start by adding the digits 4 & 6 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 4263 + 6003 = 10266.

