We have learned +, -, *, / these four operations. It is now stipulated that "★" is a new operation, and A★B means 2A-B. Then 9★6=how much.
我们学过+、-、*、/这四种运算．现在规定"★"是一种新的运算，A★B表示2A-B．那么9★6=多少．
<gadget id="calculator">2 * 9</gadget>
<output>18</output>

<gadget id="calculator">18 - 6</gadget>
<output>12</output>

<result>12</result>