Xiaoming's family is a professional rabbit breeder. They have 1440 white and black rabbits in total. The number of black rabbits is 20% less than that of white rabbits. How many white rabbits are there?
小明家是养兔专业户，白、黑兔共养了1440只，黑兔比白兔少20%，白兔有多少只？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 - (1/5)</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">1 + (4/5)</gadget>
<output>9/5 = around 1.8</output>

<gadget id="calculator">1_440 / (9/5)</gadget>
<output>800</output>

<gadget id="calculator">1_440 - 800</gadget>
<output>640</output>

<result>640</result>