Director Bao's car in the southern district of Sichen Elementary School ran out of gas and needed refueling. He took a barrel of oil and the barrel weighed 18.6 kilograms, and poured out half of the oil and the barrel weighed 9.9 kilograms. How much does this barrel weigh?
斯辰小学南区鲍主任的汽车没油了，需要加油，他拿了一桶油连桶重18.6千克，倒掉一半油连桶还重9.9千克．这个油桶重多少千克？
<gadget id="calculator">18.6 - 9.9</gadget>
<output>8.7</output>

<gadget id="calculator">8.7 * 2</gadget>
<output>17.4</output>

<gadget id="calculator">18.6 - 17.4</gadget>
<output>1.2</output>

<result>1.2</result>