We are presented with 6621 and 1146. Let's work out the sum.

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

Step 2: We'll start by adding the digits 2 & 4 in column 2 and get 6.

Step 3: We'll start by adding the digits 6 & 1 in column 3 and get 7.

Step 4: We'll start by adding the digits 6 & 1 in column 4 and get 7.

So, 6621 + 1146 = 7767.

