Beibei and Jingjing are twins, and they know that their father's current age is exactly three times the sum of their current ages. If it is also known that in 4 years, father's age will be twice the sum of their ages, how old are Beibei and Jingjing this year?
贝贝和晶晶是一对双胞胎，并且知道爸爸现在的年龄恰好是他们俩人现在年龄之和的3倍．如果还知道4年后，爸爸的年龄将等于他们两人年龄之和的2倍，则贝贝、晶晶今年都是多少岁．
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">8 - 4</gadget>
<output>4</output>

<gadget id="calculator">8 + 4</gadget>
<output>12</output>

<gadget id="calculator">3 - 2 - 2</gadget>
<output>-1</output>

<gadget id="calculator">3 + (-1)</gadget>
<output>2</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<result>6</result>