A book is priced at 75 yuan, and you can make a profit of 50% after selling it. If you sell it at 30% off the price, how much profit can you make?
一本书定价75元，售出后可获利50%，如果按定价的七折出售，可获利多少元．
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">75 * (7/10)</gadget>
<output>105/2 = around 52.5</output>

<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>

<gadget id="calculator">(105/2) - 50</gadget>
<output>5/2 = around 2.5</output>

<result>5/2 = around 2.5</result>