In April 2014, Mr. Li opened a data package of 5 yuan and 30M. As of today, 18M has been used, and how much is left unused.
2014年4月李老师办了5元30M的流量包，截止今天已经使用了18M，还剩多少没有使用．
<gadget id="calculator">30 - 18</gadget>
<output>12</output>

<gadget id="calculator">12 / 30</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">100 / 100</gadget>
<output>1</output>

<gadget id="calculator">(2/5) * 1</gadget>
<output>2/5 = around 0.4</output>

<result>2/5 = around 0.4</result>