If a repeating decimal has a repeating cycle of three digits, it will convert to a rational number with a denominator of 999.
This is because when you have a three-digit repeating decimal, like \(0.abcabcabc...\), you can express it as:
\[ x = 0.abcabcabc... \]
Multiplying both sides by \(1000\) (which shifts the decimal point three places to the right):
\[ 1000x = abc.abcabcabc... \]
Now, subtracting the original \(x\) from this equation gives:
\[ 1000x - x = abc \implies 999x = abc \]
Thus:
\[ x = \frac{abc}{999} \]
So, the answer is 999.