We've got two numbers: 2371 and 8121. Let's find their sum.

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 7 & 2 in column 2 and get 9.

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 2 & 8 in column 4 and get 10.
We'll write down the last digit 0 and carry the 1 to the next column.

So, 2371 + 8121 = 10492.

