In the given figure for <R ,the opposite side is r and the adjacent side is s.
Given r=7,s=10.
Tan of any angle is the ratio of opposite and hypotenuse.
Tan R=

Substituting values of opposite r=7 and adjacent s=10 we have:
Tan R =


R= 34.99 degrees
R= 35 degrees
Option A is the right answer.