Answer:
Angle ORP and Angle ORN are a linear pair
Explanation:
The proof will entail making use of the fact that ∠ORP and ∠ORN are supplementary. Whether their description as a linear pair is a statement or a reason will depend on your approach to the proof. Apparently, here, you are calling this fact a "statement".
The second (and subsequent) line(s) of the table might be ...
2 (statement) ORP and ORN are a linear pair. (reason) OR is a common side and R is a common vertex on line PN for these angles, hence they meet the definition of a linear pair.
3 (statement) ORP and ORN are supplementary. (reason) definition of a linear pair
4 (statement) 80 + (3x+10) = 180. (reason) substitution property; supplementary angles sum to 180 degrees
5 (statement) 3x = 90. (reason) subtraction property of equality
6 (statement) x=30. (reason) division property of equality