The sum of 2.5 times a number and 2.5 is 25. Find this number.
一个数的2.5倍与2.5的和是25，求这个数．
<gadget id="calculator">25 - 2.5</gadget>
<output>22.5</output>

<gadget id="calculator">22.5 / 2.5</gadget>
<output>9</output>

<result>9</result>