In 180/20, subtract 15 from the divisor, how much should the dividend be divided to keep the quotient constant
在180/20中，除数减去15，要使商不变，被除数应除以多少
<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<result>4</result>