Call the age gap x, so Ann is 24 minus x. When Mary was Ann’s age, x years ago, Ann was 24 minus 2x, and twice that is 24, so x is 6. Ann is 18: when Mary was 18, Ann was 12, and 24 is twice 12.
Mary is 24. She is twice as old as Ann was when Mary was as old as Ann is now. How old is Ann?
Give me a hintThe hint
The gap between their ages never changes.