When x=what, the value of 4x-18 is equal to 0.
当x=多少时，4x-18的值等于0．
<gadget id="calculator">18 + 0</gadget>
<output>18</output>

<gadget id="calculator">18 / 4</gadget>
<output>9/2 = around 4.5</output>

<result>9/2 = around 4.5</result>