To convert the repeating decimal \( 0.\overline{681} \) into a fraction, we can use the following method:
Let \( x = 0.\overline{681} \).
To eliminate the repeating part, we can multiply \( x \) by \( 1000 \) (because the repeating part is three digits long):
\[ 1000x = 681.\overline{681} \]
Now, if we subtract the original \( x \) from this equation:
\[ 1000x - x = 681.\overline{681} - 0.\overline{681} \]
This simplifies to:
\[ 999x = 681 \]
Now, we can solve for \( x \):
\[ x = \frac{681}{999} \]
So, the infinite decimal expansion \( 0.\overline{681} \) as a fraction is:
\[ \frac{681}{999} \]
You do not need to simplify it, so the final answer is:
\[ \frac{681}{999} \]