A barrel of oil is poured out three times. The first time the total (2/5) is 9 catties less, the second time the remaining (2/3) is 5 catties more, and finally the remaining 15 catties are poured out. How much is a barrel of oil?
一桶油分三次倒完，第一次倒总数的(2/5)还少9斤，第二次倒出余下的(2/3)还多5斤，最后倒出剩下的15斤，这桶油原有多少斤？
<gadget id="calculator">15 + 5</gadget>
<output>20</output>

<gadget id="calculator">2 / 3</gadget>
<output>2/3 = around 0.666667</output>

<gadget id="calculator">1 - (2/3)</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">20 / (1/3)</gadget>
<output>60</output>

<gadget id="calculator">60 - 9</gadget>
<output>51</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">51 / (3/5)</gadget>
<output>85</output>

<result>85</result>