Hari is twice as old as Johnny, who is three years older than Rahul. If Hari's age is five times Rahul's age, how old is Johnny?

Suppose the age of Johnny is F years and that of Rahul is y years. According to question Age of Hari

$\Rightarrow 2F-5y$

or $2F-5y=0$ (i)

Again F = 3 + y 

or, F - y = 3 ... (ii)

 On solving equations (i) and (ii), we get y=2

$\therefore$ Age of Johny = 3 + y = 3 + 2 = 5 years