Uncle Liu's family has 4 hectares of mountain land, and he plans to use (2/7) to plant pear trees, (1/2) to plant persimmon trees, and the rest to plant rubber trees. What percentage of the total mountain area is planted with rubber trees?
刘叔叔家有4公顷山地，他准备用其中的(2/7)种梨树，(1/2)种柿树，其它的种橡胶树．种橡胶树的面积占全部山地面积的几分之几？
<gadget id="calculator">2 / 7</gadget>
<output>2/7 = around 0.285714</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 - (2/7) - (1/2)</gadget>
<output>3/14 = around 0.214286</output>

<result>3/14 = around 0.214286</result>