40% of a number is 15, what is this number?
一个数的40%是15，这个数是多少．
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">15 / (2/5)</gadget>
<output>75/2 = around 37.5</output>

<result>75/2 = around 37.5</result>