There are 64 black rabbits and white rabbits in the rabbit farm, of which black rabbits account for 25%, and some black rabbits are bought later. Now the number of black rabbits accounts for 40% of the total number of black and white rabbits. How many black rabbits are bought again?
养兔场养黑兔和白兔共64只，其中黑兔占25%，后来又买进一些黑兔，现在黑兔数量占黑白兔总数的40%，问又买进黑兔多少只？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 64</gadget>
<output>128/5 = around 25.6</output>

<gadget id="calculator">25 / 100</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">64 * (1/4)</gadget>
<output>16</output>

<gadget id="calculator">(128/5) - 16</gadget>
<output>48/5 = around 9.6</output>

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(48/5) / (3/5)</gadget>
<output>16</output>

<result>16</result>