A number (2/5) is 210 more than its 30%, find this number.
一个数的(2/5)比它的30%多210，求这个数．
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">30 / 100</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">(2/5) - (3/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">210 / (1/10)</gadget>
<output>2_100</output>

<result>2_100</result>