The school carried out tree planting activities. The sixth grade planted 180 trees, 40 more than twice as many as the fourth grade. How many trees were planted in the fourth grade?
学校开展植树活动，六年级植树180棵，比四年级的2倍还多40棵，四年级植树多少棵？
<gadget id="calculator">160 / 2</gadget>
<output>80</output>

<result>80</result>