A rope is 9m long, use up (2/3), how much m is left
一根绳子长9m，用去(2/3)，还剩下多少m
<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">9 * (1/3)</gadget>
<output>3</output>

<result>3</result>