Potential Energy = (mass) x (gravity) x (height).
But (mass) x (gravity) is 'weight', so
Potential Energy = (weight) x (height) .
The question says that the object is 25 N .
The ' N ' stands for ' Newton ' and that's a unit of force,
so we know that this is the weight of the object.
Potential Energy = (25 N) x (3 meters)
= 75 Newton-meters
= 75 Joules .