The potential energy of a spring is given by the formula one half times spring constant times the amount that it’s been stretched squared. That’s potential… elastic potential energy. Elastic is why there’s a subscript ‘e’ on that. Okay, let’s solve that for ‘x’ and then we can take the square root of both sides and ‘trigger’ out how much it’s been stretched. So we’ll multiply both sides by two and divide both sides by ‘k’. So that gets rid of this. And take the square root of both sides as well. We get ‘x’ equals the square root of two times the potential energy in the spring divided by the spring constant. So we have square root of two times 25 Jules divided by 440 Newtons per meter. This gives us 0.337 meters which is ANSWER centimeters.