book is priced at 75 yuan, and you can make a profit of 50% after selling it. What is the cost of this book?
一本书定价75元，售出后可获利50%，这本书的成本是多少元．
<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + (1/2)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">75 / (3/2)</gadget>
<output>50</output>

<result>50</result>