Fundamental Frequency, Shortening the length of the spring

[x3lifelove]

The fundamental frequency of a spring that is 25 cm long is 441 Hz. In order to produce a fundamental frequency, using the same spring of 525 Hz, the string must be shortened to what length?

I'm honestly not even sure how to start this question. Please help :(

 

[ehild]

Assume that both ends of the string are fixed. How is related the wavelength of the standing waves to the length of the string?
How is related the wavelength to the frequency and speed of propagation?
What is fundamental frequency?

ehild