Huayuan Elementary School organized students to plant trees. The fifth grade planted 160 trees, exactly twice that of the fourth grade. The third grade had 20 fewer trees than the fourth grade, and how many trees were planted in the third grade.
花园小学组织学生植树，五年级植树160棵，正好是四年级的2倍，三年级比四年级少20棵，三年级植树多少棵．
<gadget id="calculator">160 / 2</gadget>
<output>80</output>

<gadget id="calculator">80 - 20</gadget>
<output>60</output>

<result>60</result>