Okay, we are given 7156 and 2821. Let's add them up step by step.

Step 1: We'll start by adding the digits 6 & 1 in column 1 and get 7.

Step 2: We'll start by adding the digits 5 & 2 in column 2 and get 7.

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 7 & 2 in column 4 and get 9.

So, 7156 + 2821 = 9977.

