Given: morp = 80° morn = (3x + 10)° prove: x = 30 which statement could be used in step 2 when proving x = 30? a. orp and orn are a linear pair b. orp and orn are vertical angles c. 80 = 3x +10 d. x = 30

We know that
A linear pair is a pair of adjacent angles formed when two lines intersect.
The two angles of a linear pair are always supplementary , which means their measures add up to 180°
so
ORP and ORN are a linear pair
mORP+ mORN = 180°
80°+ (3x + 10)°=180°
3x=180°-90°
x=90°/3
x=30°

therefore

the answer is the option 
A. ORP and ORN are a linear pair