A wooden stick is 80 meters long, use up (1/4), how much is left
一根木棍长80米，用去(1/4)，还剩多少
<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">1 - (1/4)</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">80 * (3/4)</gadget>
<output>60</output>

<result>60</result>