What is the present age of Mohan if the product of the ages of Mohan 5 years before and after 9 years is 15?

Let the present age of Mohan be $x$ years.Age 5 years ago = $x-5$ Age 9 years from now = $x+9$ According to the problem:
$$(x-5)(x+9)=15$$
$$x^2+9x-5x-45=15$$
$$x^2+4x-60=0$$
$$(x+10)(x-6)=0$$
Since age cannot be negative, we take $x=6$.Therefore, Mohan's present age is 6 years.