The school divides the tree planting task between the sixth grade and the fifth grade according to the ratio of 5:3. The sixth grade actually planted 108 trees, more than 20% of the original assignment. How many trees were originally planned to be planted in the fifth grade?
学校把植树任务按5：3分给六年级和五年级．六年级实际栽了108棵，超过原分配任务的20%．原计划五年级栽树多少棵？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">108 / (6/5)</gadget>
<output>90</output>

<gadget id="calculator">5 / 3</gadget>
<output>5/3 = around 1.666667</output>

<gadget id="calculator">90 / (5/3)</gadget>
<output>54</output>

<result>54</result>