Three years ago, Anne was twice as old as Bob. Today, the sum of their ages is $36$. How old is **Anne** today?

Let $a, b$ be Anne's and Bob's current ages. Three years ago: $a - 3 = 2(b - 3) \Rightarrow a = 2b - 3$. Sum today: $a + b = 36 \Rightarrow (2b - 3) + b = 36 \Rightarrow 3b = 39 \Rightarrow b = 13$. Anne $= 2(13) - 3 = 23$. Check: $3$ years ago, Anne $= 20$, Bob $= 10$, and $20 = 2 \cdot 10$ ✓. Sum today: $23 + 13 = 36$ ✓. - Trap B ($13$) is Bob's current age. - Trap C ($20$) is Anne's age $3$ years ago. - Trap A ($9$) is unrelated.