Answer:
37.4 cm
Step-by-step explanation:
The force that the spring exterts when stretched is:

Where x_0 is the relaxed length and k = 680 N/m
If a steady force of 133 N is applied when pulling the spring and elonged to a total length of 57 cm, the spring must extert the same force, but in the opposite direction, that is:

Solving for x_0
