Concept: The question tests on the basics of geometry
Solution:
A new og 2021 question
We know that the external angle is obtained as a sum of two opposite internal angles in a triangle.
=> z = x + y
St(1):- x = 50
We do not know the value of y to figure out the value of z. (Insufficient)
St(2) :- y = 35
We do not know the value of x to figure out the value of z. (Insufficient)
Combining both we have
x=50 and y =35
Thus z = x + y
= 50 + 35 (Sufficient) Option (c)