Let \( x = 0.303030...\).
To eliminate the repeating decimal, we can multiply \( x \) by 100 (since the repeating part "30" has two digits):
\[ 100x = 30.303030... \]
Now we can set up a system of equations:
- \( x = 0.303030... \)
- \( 100x = 30.303030... \)
Next, we subtract the first equation from the second:
\[ 100x - x = 30.303030... - 0.303030... \]
This simplifies to:
\[ 99x = 30 \]
Now, solve for \( x \):
\[ x = \frac{30}{99} \]
Next, we simplify the fraction \( \frac{30}{99} \). To do this, we find the greatest common divisor (GCD) of 30 and 99.
The prime factorization of 30 is \( 2 \times 3 \times 5 \) and for 99 it is \( 3^2 \times 11 \). The GCD is 3.
Now, divide both the numerator and denominator by their GCD:
\[ \frac{30 \div 3}{99 \div 3} = \frac{10}{33} \]
Thus, the repeating decimal \( 0.303030... \) can be expressed as the fraction \( \frac{10}{33} \).
In conclusion, the simplified form of the repeating decimal \( 0.30(30) \) is:
\[ \boxed{\frac{10}{33}} \]