A barrel of oil uses up 25% of its original value and buys another 84 kilograms. At this time, the weight of the oil is exactly the original (6/7). How many kilograms of oil are there?
一桶油用去原来的25%，又买来84千克，这时油的重量恰好是原来的(6/7)，原来有油多少千克？
<gadget id="calculator">6 / 7</gadget>
<output>6/7 = around 0.857143</output>

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

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

<gadget id="calculator">(6/7) - (3/4)</gadget>
<output>3/28 = around 0.107143</output>

<gadget id="calculator">84 / (3/28)</gadget>
<output>784</output>

<result>784</result>