Okay, we are tasked with adding 4121 and 3775. Let's begin!

Step 1: We'll start by adding the digits 1 & 5 in column 1 and get 6.

Step 2: We'll start by adding the digits 2 & 7 in column 2 and get 9.

Step 3: We'll start by adding the digits 1 & 7 in column 3 and get 8.

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

So, 4121 + 3775 = 7896.

