1. The problem asks for the sum of two very large numbers: 6373738838383847474746 and 883838366363366363637373. 2. To find the sum, we use the addition operation, which combines the values of the two numbers. 3. Write the numbers one under the other aligning by the rightmost digit: $$\begin{array}{r} 6373738838383847474746 \\ + 883838366363366363637373 \end{array}$$ 4. Add the numbers starting from the rightmost digit to the left, carrying over any value greater than 9 to the next digit. 5. Performing the addition: $$6373738838383847474746 + 883838366363366363637373 = 890212105201750311112119$$ 6. Therefore, the sum of the two numbers is $$890212105201750311112119$$.