I need to know the solution and the formula.

Statement:
A non-deformed spring is 15 cm long. When a 2.0 N force is applied to it, its length becomes 19 cm.
To find out:
The spring constant of the spring.
Solution:
Answer:
The spring constant of this spring is 50 N/m.
Hope you could understand.
If you have any query, feel free to ask.