The students collect tree species. The first group collected (2/5) kilograms, the second group collected (3/4) kilograms, and the third group collected less (1/2) kilograms than the total of the first and second groups. How many kilograms did the third group collect?
同学们采集树种．第一小组采集了(2/5)千克，第二小组采集了(3/4)千克，第三小组采集的比第一、二小组的总数少(1/2)千克．第三小组采集了多少千克？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">3 / 4</gadget>
<output>3/4 = around 0.75</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(3/4) - (1/2)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(2/5) + (1/4)</gadget>
<output>13/20 = around 0.65</output>

<result>13/20 = around 0.65</result>