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