Sure thing! We've got 2115 and 7821 and we're gonna add them together.

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

Step 2: We'll start by adding the digits 1 & 2 in column 2 and get 3.

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

Step 4: We'll start by adding the digits 2 & 7 in column 4 and get 9.

So, 2115 + 7821 = 9936.

