If a piece of 30 hectares of land has been cultivated and 18 hectares have been cultivated, what is the formula for finding the percentage left uncultivated?
耕一块30公顷的地，已耕了18公顷，求还有百分之几未耕的算式是多少
<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<gadget id="calculator">12 / 30</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>