Xiaoming's mother bought a fish for 8 yuan, sold it for 9 yuan, and then bought it back for 10 yuan, and sold it to another person for 11 yuan. How much money did Xiaoming's mother earn?
小明妈妈花8元买了一条鱼，以9元价格卖掉，然后觉得不合算，又花10元买回来，以11元卖给另一个人，那么小明妈妈赚了多少元．
<gadget id="calculator">8 + 10</gadget>
<output>18</output>

<gadget id="calculator">9 - 18</gadget>
<output>-9</output>

<gadget id="calculator">11 + (-9)</gadget>
<output>2</output>

<result>2</result>