We've got two numbers: 8098400842 and 4585436546. Let's find their sum.

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

Step 2: We'll start by adding the digits 4 & 4 in column 2 and get 8.

Step 3: We'll start by adding the digits 8 & 5 in column 3 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 4: We'll start by adding the digits 0 & 6 in column 4 and get 7.

Step 5: We'll start by adding the digits 0 & 3 in column 5 and get 3.

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

Step 7: We'll start by adding the digits 8 & 5 in column 7 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 8: We'll start by adding the digits 9 & 8 in column 8 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

Step 9: We'll start by adding the digits 0 & 5 in column 9 and get 6.

Step 10: We'll start by adding the digits 8 & 4 in column 10 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

So, 8098400842 + 4585436546 = 12683837388.

