There are 35 white rabbits, and the number of black rabbits is less than that of white rabbits (1/7). How many black rabbits are there?
白兔有35只，黑兔的只数比白兔少(1/7)，黑兔多少只？
<gadget id="calculator">1 / 7</gadget>
<output>1/7 = around 0.142857</output>

<gadget id="calculator">1 - (1/7)</gadget>
<output>6/7 = around 0.857143</output>

<gadget id="calculator">35 * (6/7)</gadget>
<output>30</output>

<result>30</result>