A ticket to the stadium is 30 yuan. If the audience increases by half after the price is reduced, but the income only increases by 25%, how much is the price of each ticket reduced?
体育场入场券30元一张，若降价后观众增加一半而收入却只增加25%，每张入场券降价多少元．
<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">30 * (1/4)</gadget>
<output>15/2 = around 7.5</output>

<gadget id="calculator">30 + (15/2)</gadget>
<output>75/2 = around 37.5</output>

<gadget id="calculator">1 / 2</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">(75/2) / (3/2)</gadget>
<output>25</output>

<gadget id="calculator">30 - 25</gadget>
<output>5</output>

<result>5</result>