A bottle of oil weighs 40 grams. If half of the oil is eaten, the weight of the bottle is 25 grams. How many grams does the bottle weigh?
一瓶油连瓶重40克，吃去一半油，连瓶重25克，瓶有多少克．
<gadget id="calculator">40 - 25</gadget>
<output>15</output>

<gadget id="calculator">15 * 2</gadget>
<output>30</output>

<gadget id="calculator">40 - 30</gadget>
<output>10</output>

<result>10</result>