Uncle Zhang’s family contracted a barren hill, 20% of which were planted with fruit trees, and the remaining 120 hectares were all planted with pine trees. How many hectares of barren hills did his family contract?
张大伯家承包了一片荒山，其中20%种果树，其余的120公顷全部种松树，他家承包的荒山总面积是多少公顷？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">120 / (4/5)</gadget>
<output>150</output>

<result>150</result>