We are presented with 4998768946 and 8645685876. Let's work out the sum.

Step 1: We'll start by adding the digits 6 & 6 in column 1 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 2: We'll start by adding the digits 4 & 7 in column 2 and get 12.
We'll write down the last digit 2 and carry the 1 to the next column.

Step 3: We'll start by adding the digits 9 & 8 in column 3 and get 18.
We'll write down the last digit 8 and carry the 1 to the next column.

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

Step 5: We'll start by adding the digits 6 & 8 in column 5 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

Step 6: We'll start by adding the digits 7 & 6 in column 6 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 7: We'll start by adding the digits 8 & 5 in column 7 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 8: We'll start by adding the digits 9 & 4 in column 8 and get 14.
We'll write down the last digit 4 and carry the 1 to the next column.

Step 9: We'll start by adding the digits 9 & 6 in column 9 and get 16.
We'll write down the last digit 6 and carry the 1 to the next column.

Step 10: We'll start by adding the digits 4 & 8 in column 10 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

So, 4998768946 + 8645685876 = 13644454822.

