Concept:
Beat frequency is equal to the absolute difference between the frequencies of two sound sources.
\[
f_b=|f_P-f_R|
\]
Step 1: Express the frequencies in terms of \(f_Q\).
Let the frequency of tuning fork \(Q\) be \(f\).
Then,
\[
f_P=f+1.5%f
\]
\[
f_P=1.015f
\]
Similarly,
\[
f_R=f-2.5%f
\]
\[
f_R=0.975f
\]
Step 2: Use the beat frequency relation.
Given,
\[
f_b=8Hz
\]
Therefore,
\[
1.015f-0.975f=8
\]
\[
0.04f=8
\]
\[
f=200Hz
\]
Step 3: Calculate the frequency of tuning fork R.
\[
f_R=0.975(200)
\]
\[
f_R=195Hz
\]
Thus, the frequency of tuning fork \(R\) is
\[
\boxed{195Hz}
\]