Xiao Gang is 30 years younger than his father. How old is Xiao Gang when his father is three times his age? (solution by equation)
小刚比爸爸小30岁，当爸爸的年龄是小刚的3倍时，小刚几岁？(用方程解)
<gadget id="calculator">3 - 1</gadget>
<output>2</output>

<gadget id="calculator">30 / 2</gadget>
<output>15</output>

<result>15</result>