There are the same number of white rabbits and black rabbits in the farm. In June, 240 black rabbits were sold and 300 white rabbits were bought back. At this time, the ratio of white rabbits to black rabbits was 7:4. How many black rabbits and white rabbits are there?
养殖场中有同样多的白兔和黑兔，六月份，卖掉黑兔240只，又买回白兔300只，这时，白兔与黑兔的比是7：4，养殖场原有黑兔和白兔各多少只？
<gadget id="calculator">7 / 4</gadget>
<output>7/4 = around 1.75</output>

<gadget id="calculator">(7/4) * 240</gadget>
<output>420</output>

<gadget id="calculator">300 + 420</gadget>
<output>720</output>

<gadget id="calculator">(7/4) - 1</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">720 / (3/4)</gadget>
<output>960</output>

<result>960</result>