The school assigns the tree planting task to the fifth and sixth grades at a ratio of 3:5. The sixth grade actually planted 156 trees, equivalent to 120% of its original assignment. How many trees were originally planned to be planted in the fifth grade?
学校把植树任务按3：5分配给五年级和六年级．六年级实际植树156棵，相当于它原分配任务的120%．原计划五年级植树多少棵？
<gadget id="calculator">120 / 100</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">3 + 5</gadget>
<output>8</output>

<gadget id="calculator">5 / 8</gadget>
<output>5/8 = around 0.625</output>

<gadget id="calculator">156 / (6/5) / (5/8)</gadget>
<output>208</output>

<gadget id="calculator">3 / 8</gadget>
<output>3/8 = around 0.375</output>

<gadget id="calculator">208 * (3/8)</gadget>
<output>78</output>

<result>78</result>