Eden's mom is twice as old as Eden, who is twice as old as Devin. If Devin is 12 years old, what's the average age of the three?
If Devin is 12 years old, then Eden is 2 * 12 years = 24 years old.
Since Eden's mom two times older than Eden, her age is 24 years * 2 = 
<gadget id="calculator">24*2</gadget>
<output>48</output>
48 years.
In total, they have 48 years + 24 years + 12 years = 
<gadget id="calculator">48+24+12</gadget>
<output>84</output>
84 years.
The average age for the three is 84 years / 3 people = 
<gadget id="calculator">84/3</gadget>
<output>28</output>
28 years/person.

<result>28</result>