If x*(5/7)=y*(1/9)=1 (both x and y are not 0), then 25x-2y=how much.
如果x*(5/7)=y*(1/9)=1(x与y都不为0)，那么25x-2y=多少．
<gadget id="calculator">7 / 5</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">25 * (7/5)</gadget>
<output>35</output>

<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<gadget id="calculator">35 - 18</gadget>
<output>17</output>

<result>17</result>