Okay, we are tasked with adding 3860 and 3431. Let's begin!

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

Step 2: We'll start by adding the digits 6 & 3 in column 2 and get 9.

Step 3: We'll start by adding the digits 8 & 4 in column 3 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

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

So, 3860 + 3431 = 7291.

