For a barrel of oil, half of the oil is used for the first time, and the remaining half is used for the second time, which is 15 kilograms more, and 12 kilograms are left in the end. How many kilograms does the barrel of oil originally weigh?
一桶油，第一次用去全部的一半，第二次用去余下的一半还多15千克，最后剩下12千克，这桶油原来重多少千克？
<gadget id="calculator">12 + 15</gadget>
<output>27</output>

<gadget id="calculator">27 * 2 * 2</gadget>
<output>108</output>

<result>108</result>