2 tons of cement, use up (1/4), how many tons are left?
2吨水泥，用去(1/4)，还剩多少吨？
<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">2 * (3/4)</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>