Given that the middle term of the ratio between 6 and x is 4, then x=how much.
已知6与x的比例中项为4，则x=多少．
<gadget id="calculator">4 * 4</gadget>
<output>16</output>

<gadget id="calculator">16 / 6</gadget>
<output>8/3 = around 2.666667</output>

<result>8/3 = around 2.666667</result>