Okay, we are given 3801 and 5121. Let's add them up step by step.

Step 1: We'll start by adding the digits 1 & 1 in column 1 and get 2.

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

Step 3: We'll start by adding the digits 8 & 1 in column 3 and get 9.

Step 4: We'll start by adding the digits 3 & 5 in column 4 and get 8.

So, 3801 + 5121 = 8922.

