Please solve the problem

let the frequency of the tuning fork be n.

Here beats are produced between the vibrating string and tuning fork, and later on beats are heard once again on decreasing the tension.

(n+5) = 1/2L sq root of (T₁/m)   ----(1)

When the tension is reduced the frequency also gets reduced.

(n-5) = 1/2L sq root of T₂/m. -----(2)

L and m do not change as the wire is not being changed, only the tension in it is decreased.

take ratio of above two equations and solve for n.

If you have not understand any particular step you can write to me.