Explanation:

R’s position from the right end = 10^th
It is given that there are 10 people between R and P, therefore,
P cannot be at right side of R, as there are only 9 people at the right side of R. So P will at the left side of R.
Now, P's position from right end = R's position from the right end + 10 + 1 = 10 + 10 + 1 = 21st from the right end.
Now, we can find P’s position from the left end as:
P’s position from the left end = Total number of people – P's position from the right end – 1 = 35 – 21 – 1 = 15^th