We are presented with 8101 and 664. Let's work out the sum.

Step 1: We'll start by adding the digits 1 & 4 in column 1 and get 5.

Step 2: We'll start by adding the digits 0 & 6 in column 2 and get 6.

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

Step 4: We'll start by adding the digits 8 & 0 in column 4 and get 8.

So, 8101 + 664 = 8765.

