Question 1
In 7 years, Radha will be twice as old as Charlotte was 3 years ago. If Charlotte is 18 now, how old is Radha now?
In 7 years: Radha=Radha(now)+7, Charlotte was 18-3=15 three years ago. Radha(now)+7=2*15 => Radha(now) = 2*15 - 7 = 23.