No problem, let's work through this together. We're starting with 8243081263 and 7640166886 and adding them all up.

Step 1: We'll start by adding the digits 3 & 6 in column 1 and get 9.

Step 2: We'll start by adding the digits 6 & 8 in column 2 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 2 & 8 in column 3 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 1 & 6 in column 4 and get 8.

Step 5: We'll start by adding the digits 8 & 6 in column 5 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 6: We'll start by adding the digits 0 & 1 in column 6 and get 2.

Step 7: We'll start by adding the digits 3 & 0 in column 7 and get 3.

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

Step 9: We'll start by adding the digits 2 & 6 in column 9 and get 8.

Step 10: We'll start by adding the digits 8 & 7 in column 10 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 8243081263 + 7640166886 = 15883248149.

