The age of each sister is $(32-8) \div 3 =8$ years old. Thus, Alex is $8 +8 =16$ years old. 
Alex is $8$ years older than her two sisters who are twins. The sum of the ages of all three girls is $32$ years old. How old is Alex? ($2007$ Math Kangaroo Problem, Level $5$-$6$, Question \#$9$) 

[a] $$12$$ 
[b] $$18$$ 
[c] $$16$$ 
[d] $$20$$ 
[e] $$14$$ 