After a barrel of oil is used (2/5), another 15 kg is added, and the oil at this time is exactly 80% of the original amount. How much oil is there in the oil barrel?
一桶油，用去(2/5)后，又加进了15千克，这时的油正好是原来的80%，油桶里现有多少油？
<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

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

<gadget id="calculator">1 - (2/5)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">(4/5) - (3/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">15 / (1/5)</gadget>
<output>75</output>

<gadget id="calculator">75 * (4/5)</gadget>
<output>60</output>

<result>60</result>