Applying the definition of vertical angles, the measure of angle 4 is: 144°.
What are Vertical Angles?
Vertical angles are a pair of angles that lie directly opposite each other and are equal in measure to each other.
m∠1 + m∠2 = 180° (linear pair)
Substitute
3x + 12x = 180
15x = 180
x = 12
∠4 and ∠2 are vertical angles, therefore:
m∠4 = m∠2 = 12x
Plug in the value of x
m∠4 = 12(12)
m∠4 = 144°
Therefore, applying the definition of vertical angles, the measure of angle 4 is: 144°.
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