Let's solve this addition problem. We have 6666 and 8112, and we need to add them together.

Step 1: We'll start by adding the digits 6 & 2 in column 1 and get 8.

Step 2: We'll start by adding the digits 6 & 1 in column 2 and get 7.

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 & 8 in column 4 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

So, 6666 + 8112 = 14778.

