If the value of 6x-18 is 42, what is the value of 4x-18.
如果6x-18的值是42，那么4x-18的值是多少．
<gadget id="calculator">42 + 18</gadget>
<output>60</output>

<gadget id="calculator">60 / 6</gadget>
<output>10</output>

<gadget id="calculator">4 * 10</gadget>
<output>40</output>

<gadget id="calculator">40 - 18</gadget>
<output>22</output>

<result>22</result>