Answer:
![f_(frequency)=483Hz](https://img.qammunity.org/2021/formulas/physics/high-school/mv3iyuhc2t7gs0sje3pzjasrlwjh4q9y1j.png)
Step-by-step explanation:
Let f is frequency of of the guitar string
Frequency of tuning fork is given 487 Hz
Beat frequency is difference frequencies of guitar string and the tuning fork
It could be
(f - 487Hz)
or
(487Hz-f)
As it is mentioned that as the frequency of guitar string increases the beat frequency decreases
So the beat frequency is given as
![f_(frequency)=(487Hz-f)\\f_(frequency)=(487-4)\\ f_(frequency)=483Hz](https://img.qammunity.org/2021/formulas/physics/high-school/d8jvy8scxdwj9ode1awvzhbmaoccssej3z.png)