To convert the repeating decimal \( 0.18\overline{18} \) to a fraction, we can use the following steps:
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Let \( x = 0.181818\ldots \).
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To eliminate the repeating part, we can multiply both sides of the equation by 100 (which shifts the decimal point two places to the right): \[ 100x = 18.181818\ldots \]
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Now, we can set up the equation: \[ 100x = 18 + x \]
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Subtract \( x \) from both sides: \[ 100x - x = 18 \] \[ 99x = 18 \]
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Now, solve for \( x \): \[ x = \frac{18}{99} \]
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To simplify \( \frac{18}{99} \), we can divide the numerator and the denominator by their greatest common divisor (GCD), which is 9: \[ \frac{18 \div 9}{99 \div 9} = \frac{2}{11} \]
Thus, the repeating decimal \( 0.18\overline{18} \) as a fraction in simplest form is
\[ \boxed{\frac{2}{11}}. \]