Subtract (2/5) from 3 times a number, the difference is 5.2, find this number.
一个数的3倍减去它的(2/5)，差是5.2，求这个数．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 - (2/5)</gadget>
<output>13/5 = around 2.6</output>

<gadget id="calculator">5.2 / (13/5)</gadget>
<output>2</output>

<result>2</result>