The original price of a commodity is 120 yuan, and it is sold at a 25% discount, which is how much cheaper.
一种商品原价120元，按七五折销售，便宜了多少元．
<gadget id="calculator">75 / 100</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 - (3/4)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">120 * (1/4)</gadget>
<output>30</output>

<result>30</result>