Subtract (2/3) of a number from 20, the difference is 15, what is this number?
从20里面减去一个数的(2/3)，差是15，这个数是多少？
<gadget id="calculator">25 - 15</gadget>
<output>10</output>

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

<gadget id="calculator">10 / (2/3)</gadget>
<output>15</output>

<result>15</result>