☆Indicates a new operation, and stipulates that a☆b=2a+3b, then (3☆4)☆5=how much.
☆表示一种新的运算，并且规定a☆b=2a+3b，那么(3☆4)☆5=多少．
<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">3 * 4</gadget>
<output>12</output>

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

<gadget id="calculator">18 * 2</gadget>
<output>36</output>

<gadget id="calculator">3 * 5</gadget>
<output>15</output>

<gadget id="calculator">36 + 15</gadget>
<output>51</output>

<result>51</result>