Mom's age is 3.8 times that of Hong Hong's, father's age is 4.2 times that of Hong Hong's, father is 4 years older than mother, how old is Hong Hong this year?
妈妈的年龄是红红的3.8倍，爸爸的年龄是红红的4.2倍，爸爸比妈妈大4岁，红红今年几岁？
<gadget id="calculator">4.2 - 3.8</gadget>
<output>0.4</output>

<gadget id="calculator">4 / 0.4</gadget>
<output>10</output>

<result>10</result>