Suppose a★b=3a-2b, given that X★(4★1)=7, then X=how much.
设a★b=3a-2b，已知X★(4★1)=7，则X=多少．
<gadget id="calculator">3 * 4</gadget>
<output>12</output>

<gadget id="calculator">2 * 1</gadget>
<output>2</output>

<gadget id="calculator">12 - 2</gadget>
<output>10</output>

<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">7 + 20</gadget>
<output>27</output>

<gadget id="calculator">27 / 3</gadget>
<output>9</output>

<result>9</result>