Representing ages

Alex will be twice as old as Bill in three years. Write an expression which correctly describes
Alex’s present age in terms of Bill’s present age, b?

b = Bill's age in 3 years
2b = Alex's age in 3 years {Alex will be twice as old as Bill in 3 years} 

If Bill is b in 3 years, then he is b - 3 right now.
Also, if Alex is 2b in 3 years, then he is 2b - 3 right now. 

Alex's present age is 2b - 3


- Algebra House