It is known that 3x+9=15, then 7x-8=how much.
已知3x+9=15，那么7x-8=多少．
<gadget id="calculator">15 - 9</gadget>
<output>6</output>

<gadget id="calculator">6 / 3</gadget>
<output>2</output>

<gadget id="calculator">7 * 2</gadget>
<output>14</output>

<gadget id="calculator">14 - 8</gadget>
<output>6</output>

<result>6</result>