Okay, we are given 6647426194 and 9343888031. Let's add them up step by step.

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 9 & 3 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 1 & 0 in column 3 and get 2.

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.

Step 5: We'll start by adding the digits 2 & 8 in column 5 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 6: We'll start by adding the digits 4 & 8 in column 6 and get 13.
We'll write down the last digit 3 and carry the 1 to the next column.

Step 7: We'll start by adding the digits 7 & 3 in column 7 and get 11.
We'll write down the last digit 1 and carry the 1 to the next column.

Step 8: We'll start by adding the digits 4 & 4 in column 8 and get 9.

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

Step 10: We'll start by adding the digits 6 & 9 in column 10 and get 15.
We'll write down the last digit 5 and carry the 1 to the next column.

So, 6647426194 + 9343888031 = 15991314225.

