(2/3) of a number is equal to (4/5) of 15, find this number.
一个数的(2/3)与15的(4/5)相等，求这个数．
<gadget id="calculator">4 / 5</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">15 * (4/5)</gadget>
<output>12</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">12 / (2/3)</gadget>
<output>18</output>

<result>18</result>