Buy a T-shirt, the original price is 80 yuan, how much is it if you sell it with a 20% discount?
买一件T恤衫，原价80元，如果打八折出售是多少元？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">80 * (4/5)</gadget>
<output>64</output>

<result>64</result>