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If lines a and b are parallel, what is the value of x?

If lines a and b are parallel, what is the value of x?-example-1
User Tuan Chau
by
8.7k points

1 Answer

3 votes

Answer: 60 (choice D)

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Step-by-step explanation:

Let y be the angle just to the left of angle x. Angle x and angle y are adjacent.

Since line a is parallel to line b, this means y = 120 because the 120 degree angle and angle y are alternate interior angles.

Then we can say:

x+y = 180

x+120 = 180

x = 180-120

x = 60

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An alternative method:

Let w be the angle just above angle x

The angle marked "120 degrees" and angle w are corresponding angles. They are congruent if and only if line a is parallel to line b.

This makes w = 120

Solving w+x = 180 leads to x = 60 similar to the previous set of steps.

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Side note:

The 115 degree angle is never used. It was probably put in there as a distraction.

User YogeshR
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