Official solution
Contrapositive of p \[ \to \] q is \[ \sim \]q \[ \to \] \[ \sim \]p.
Here,
Let
p = Side of a square is doubles.
q = Area of square increases four times.
\[ \therefore \] \[ \sim \]q \[ \to \] \[ \sim \]p = If the area of a square does not increase four times, then its side is not doubled.