Huanhuan and his father are 54 years old together, and his father's age is 3.5 times that of Huanhuan. How old is Huanhuan this year? (solution by equation)
欢欢和他爸爸今年的年龄一共是54岁，爸爸的年龄是欢欢的3.5倍，欢欢今年多少岁？(用方程解)
<gadget id="calculator">1 + 3.5</gadget>
<output>4.5</output>

<gadget id="calculator">54 / 4.5</gadget>
<output>12</output>

<result>12</result>