30% off basketball at sporting goods stores. It used to cost 50 yuan to buy a basketball, how much does it cost now?
体育用品商店篮球打七折出售．原来买1只篮球需花50元，现在需要多少元．
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">50 * (7/10)</gadget>
<output>35</output>

<result>35</result>