A number minus its 0.84 times, the difference is 4, find this number.
一个数减去它的0.84倍，差是4，求这个数．
<gadget id="calculator">1 - 0.84</gadget>
<output>0.16</output>

<gadget id="calculator">4 / 0.16</gadget>
<output>25</output>

<result>25</result>