To find the percentage of land available for farming, you can use the formula:
\[ \text{Percentage} = \left( \frac{\text{Area for farming}}{\text{Total area}} \right) \times 100 \]
In this case, the area for farming is 20 acres and the total area is 30 acres.
\[ \text{Percentage} = \left( \frac{20}{30} \right) \times 100 = \frac{2}{3} \times 100 \approx 66.67% \]
So, the percentage of the land that is available for farming is approximately 66.66%.