 A $6\text{-year stock}$ that goes up $30\%$ in the first year, down $30\%$ in the second, up $30\%$ in the third, down $30\%$ in the fourth, up $30\%$ in the fifth, and down $30\%$ in the sixth is equivalent to a $3\text{-year stock}$ that loses $x\%$ in each of its three years. Compute $x$.

1. Let the initial price of the stock be \( a \).

2. Calculate the price of the stock at the end of each year:
   - After the first year, the stock goes up by 30%:
     \[
     a \times 1.3
     \]
   - After the second year, the stock goes down by 30%:
     \[
     a \times 1.3 \times 0.7 = a \times 0.91
     \]
   - After the third year, the stock goes up by 30%:
     \[
     a \times 0.91 \times 1.3 = a \times 1.183
     \]
   - After the fourth year, the stock goes down by 30%:
     \[
     a \times 1.183 \times 0.7 = a \times 0.8281
     \]
   - After the fifth year, the stock goes up by 30%:
     \[
     a \times 0.8281 \times 1.3 = a \times 1.07653
     \]
   - After the sixth year, the stock goes down by 30%:
     \[
     a \times 1.07653 \times 0.7 = a \times 0.753571
     \]

3. The final price of the stock after 6 years is:
   \[
   a \times 0.753571
   \]

4. We need to find \( x \) such that a 3-year stock that loses \( x\% \) each year results in the same final price. Let the initial price be \( a \). After 3 years, the price is:
   \[
   a \times (1 - \frac{x}{100})^3
   \]

5. Set the final prices equal to each other:
   \[
   a \times 0.753571 = a \times (1 - \frac{x}{100})^3
   \]

6. Simplify by dividing both sides by \( a \):
   \[
   0.753571 = (1 - \frac{x}{100})^3
   \]

7. Take the cube root of both sides:
   \[
   \sqrt[3]{0.753571} = 1 - \frac{x}{100}
   \]

8. Calculate the cube root:
   \[
   \sqrt[3]{0.753571} \approx 0.912
   \]

9. Solve for \( x \):
   \[
   0.912 = 1 - \frac{x}{100}
   \]
   \[
   \frac{x}{100} = 1 - 0.912
   \]
   \[
   \frac{x}{100} = 0.088
   \]
   \[
   x = 8.8
   \]

The final answer is \( \boxed{8.8} \).