Answer:
a) a straight angle measures 180°
b) a linear pair is composed of two (2) angles
c) adjacent angles share a side
Explanation:
These questions rely on your familiarity with the angle addition postulate, the definition of a linear (or straight) angle, and the definition of adjacent angles.
A Sum is 180°
Angles 1 through 4 total 180° because their combined effect is to form angle GHJ, which is a straight angle. That is, vertex H is on line segment GJ.
A straight angle always measures 180°. The angles can be added according to the Angle Addition Postulate, which effectively tells you the whole is the sum of the parts.
B Linear pair
A linear pair is two angles that together form a straight angle. Here, we have four angles involved. No two of them form a straight angle, so there are no linear pairs in this diagram.
C Adjacent angles
Adjacent angles share a vertex and one side. Angles 1 and 3 are non-adjacent, because they do not share a side. (The shared side must be interior to the other two sides.)