According to 2X+1=8, how much is 4X-1 equal to?
根据2X+1=8，求4X-1等于多少．
<gadget id="calculator">8 - 1</gadget>
<output>7</output>

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

<gadget id="calculator">14 - 1</gadget>
<output>13</output>

<result>13</result>