A certain number minus 10% of it is equal to (1/3) of 210, what is the certain number?
某数减去它的10%，等于210的(1/3)，求某数是多少？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">210 * (1/3)</gadget>
<output>70</output>

<gadget id="calculator">10 / 100</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 - (1/10)</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">70 / (9/10)</gadget>
<output>700/9 = around 77.777778</output>

<result>700/9 = around 77.777778</result>