What would you get if you replace 'a' with 23 in the expression representing Shabnam’s age?

If Aftab's age is represented by the letter 'a' and Shabnam’s age is 3 years older, how can we express Shabnam’s age?

If 's' represents Shabnam’s age and Aftab is 3 years younger, what expression represents Aftab’s age?

If Aftab is currently 18 years old, what is Shabnam’s age?

Which of the following is an algebraic expression for Aftab's age if Shabnam's age is 23?