Question

Name the relationship between the angles below. What is the sum of the angles? Explain how you would find the missing angle. Explain each step. (replace with 120 & x)

Answer 1

• linear pair; supplementary angles
• sum is 180°
• subtract the known angle from 180°

Explanation:

Angles that form a straight line are called a linear pair. They are supplementary angles (by definition), so their sum is 180°.

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Replacing the angle numbers with their values, we can use this relationship.

120 + x = 180 . . . . use the given numbers in the supplementary angle relationship

x = 180 -120 . . . . . use the addition property of equality to find x by subtracting 120 from both sides of the equation

x = 60

The missing angle (x) is 60 degrees.