There is a barrel of oil in the cafeteria. After eating it (9/10), another 12 kilograms are bought. The oil at this time is equivalent to 20% of the oil consumed. How many kilograms of oil did the cafeteria have?
食堂有一桶油，吃去(9/10)后，又买来12千克，这时的油相当于吃去的20%，食堂原有多少千克油？
<gadget id="calculator">9 / 10</gadget>
<output>9/10 = around 0.9</output>

<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(9/10) * (1/5)</gadget>
<output>9/50 = around 0.18</output>

<gadget id="calculator">1 - (9/10)</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">(9/50) - (1/10)</gadget>
<output>2/25 = around 0.08</output>

<gadget id="calculator">12 / (2/25)</gadget>
<output>150</output>

<result>150</result>