Four times of 4.5 is 1.8 more than 1.2 times of a number. Find this number.
4.5的4倍比一个数的1.2倍多1.8，求这个数．
<gadget id="calculator">4.5 * 4</gadget>
<output>18</output>

<gadget id="calculator">18 - 1.8</gadget>
<output>16.2</output>

<gadget id="calculator">16.2 / 1.2</gadget>
<output>13.5</output>

<result>13.5</result>