List the ratio and solve the ratio: the ratio of 12 to 4 is equal to the ratio of x to 9.
列出比例式并解比例：12和4的比值与x和9的比值相等．
<gadget id="calculator">12 * 9</gadget>
<output>108</output>

<gadget id="calculator">108 / 4</gadget>
<output>27</output>

<result>27</result>