A barrel of oil weighs 16 kilograms, and when half of it is used, the weight of the barrel is 9 kilograms. How many kilograms of original oil?
一桶油连桶重16千克，用去一半后，连桶重9千克．原有油多少千克？
<gadget id="calculator">16 - 9</gadget>
<output>7</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<result>14</result>