Aunt Li's family bought a barrel of Golden Dragon Oil, which was used in January (7/20), and (2/5) in February, leaving (5/2) kilograms. How many kilograms is this barrel of oil originally?
李阿姨家买来一桶金龙油，一月份用去这桶油的(7/20)，二月份用去这桶油的(2/5)，剩(5/2)千克．这桶油原来有多少千克？
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">7 / 20</gadget>
<output>7/20 = around 0.35</output>

<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">1 - (7/20) - (2/5)</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(5/2) / (1/4)</gadget>
<output>10</output>

<result>10</result>