(1/7) of a number is 9 less than its (2/5), what is this number?
一个数的(1/7)比它的(2/5)少9，这个数是多少？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">(2/5) - (1/7)</gadget>
<output>9/35 = around 0.257143</output>

<gadget id="calculator">9 / (9/35)</gadget>
<output>35</output>

<result>35</result>