12 plus (2/5) of a number, the sum is 18, what is this number
12加上一个数的(2/5)，和是18，这个数是多少
<gadget id="calculator">18 - 12</gadget>
<output>6</output>

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

<gadget id="calculator">6 / (2/5)</gadget>
<output>15</output>

<result>15</result>