In a ratio, the two outer terms are 3 and 9, one of the inner terms is 6, and the other inner term is what.
在一个比例里，两个外项是3和9，其中一个内项是6，另一个内项是多少．
<gadget id="calculator">3 * 9</gadget>
<output>27</output>

<gadget id="calculator">27 / 6</gadget>
<output>9/2 = around 4.5</output>

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