The sum of 1.5 times of a number plus 18 is equal to its 3 times. Find this number. (solution by equation)
一个数的1.5倍加上18的和等于它的3倍，求这个数．(用方程解)
<gadget id="calculator">3 - 1.5</gadget>
<output>1.5</output>

<gadget id="calculator">18 / 1.5</gadget>
<output>12</output>

<result>12</result>