Suppose A◎B=3A-2B, and X◎(4◎1)=7 is known, so what is X◎4=
假设A◎B=3A一2B，已知X◎(4◎1)=7，那么X◎4=多少
<gadget id="calculator">3 * 9</gadget>
<output>27</output>

<gadget id="calculator">2 * 4</gadget>
<output>8</output>

<gadget id="calculator">27 - 8</gadget>
<output>19</output>

<result>19</result>