let x = Edna's age
then it follows that (x + 1) is Ellie's age and (x + 2) is Elsa's age
We can now write and equation for the sum of their ages equal to 108:
x + (x + 1) + (x +2) = 108 simplify the left side
3x + 3 = 108 subtract 3 from both sides
3x = 105 divide both sides by 3
x = 35
Edna is 35, Ellie is 36, and Elsa is 37
