A 30% discount on a piece of clothing is how much it is lower than the original price.
一件衣服打7折，就是比原价降多少．
<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">1 - (7/10)</gadget>
<output>3/10 = around 0.3</output>

<result>3/10 = around 0.3</result>