Aspring requires a force of 25 n to produce an extension of 2 cm in it. what is the work done in further extending it by 3 cm.

25/2=12.5
12.5 N is equal to 1 centimeter
Plug in 12.5 in for whatever the value of the centimeter is

Example
i want to know how many Newtons of force are needed to get 5 cm of extension

12.5*5=62.5

This is all i've got for your question because its not very specific. 

Good Luck

25 = k (0.02)
k = 1250

We use the work formula which is force times the distance resulting to the expression:

W = (1/2)(kx^2)
W = (1/2)(1250)(0.03^2)
W = 0.5625 J

Ithink they do have the same properties just in less quantities i think