Q) The product of Rehan’s age (in years) 5 years ago and his age 7 years from now, is one more than twice his present age. Find his present age.
Ans: Let’s consider Rehan’s present age is X.
Age 5 years ago = X – 5
Age 7 years from now = X + 7
Product of these 2 points: (X – 5) ( X + 7)
By given condition, (X – 5) (X + 7) – 1 = 2 x
∴ X2 + 2 X – 35 – 1 = 2 X
∴ X2 = 36
∴ X = 6, – 6
∵ Age can not be negative, ∴ Value of X 
– 6,
∴ X = 6
Therefore, Rehan’s present age is 6.