OK, let's do this. We've got 3664 and 201 and we're adding them all together.

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

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

Step 3: We'll start by adding the digits 6 & 2 in column 3 and get 8.

Step 4: We'll start by adding the digits 3 & 0 in column 4 and get 3.

So, 3664 + 201 = 3865.

