Answer is in the screenshot.
The 3 inside angles need to equal 180.
Subtract E from 180 to find the sum of the other two angles:
180 - 104 = 76
Now because EF ≅ DE , angle D and F would be the same so divide 76 by 2
Angle D = 38
The range would be the difference between the lowest age and the highest age.
The highest age is 76, the lowest age is 30
The range is 76 - 30 = 46