jacket is a yuan, a pair of trousers is less than a jacket (2/5) b yuan, how much is a pair of trousers.
一件上衣a元，一件裤子比一件上衣的(2/5)少b元，一件裤子多少元．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>