80% of a number is 2.4, what is 30% of this number?
一个数的80%是2.4，这个数的30%是多少．
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">2.4 / (4/5)</gadget>
<output>3</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">3 * (3/10)</gadget>
<output>9/10 = around 0.9</output>

<result>9/10 = around 0.9</result>