A book is priced at 36 yuan, and the profit is 20% of the cost. How much is the cost?
一本书售价36元，利润是成本的20%，成本是多少元？
<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">36 / (6/5)</gadget>
<output>30</output>

<result>30</result>