A jacket is 420 yuan, and the trousers are cheaper than the jacket (3/7), how much is the trousers cheaper than the jacket.
一件上衣420元，裤子比上衣便宜(3/7)，裤子比上衣便宜多少元．
<gadget id="calculator">3 / 7</gadget>
<output>3/7 = around 0.428571</output>

<gadget id="calculator">420 * (3/7)</gadget>
<output>180</output>

<result>180</result>