A number (2/5) plus 2.8 equals 12.8, find this number.
一个数的(2/5)加上2.8等于12.8，求这个数．
<gadget id="calculator">12.8 - 2.8</gadget>
<output>10</output>

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

<gadget id="calculator">10 / (2/5)</gadget>
<output>25</output>

<result>25</result>