The measurement of ∠B is 168°
Given,
In the question:
Angle A and Angle B are supplementary angles.
If mA (x - 9)° and m/B= (7x + 21)°
To find the measure of ∠B
Now, According to the question;
What are supplementary angles?
Two angles are Supplementary when they add up to 180 degrees.
Now, ∠A+∠B = 180°
So,
⇒(x - 9)˚+(7x + 21)°=180°
=> 8x +12 = 180°
=> 8x = 180° - 12
=> 8x = 168
=> x = 168/8
=> x = 21
For the measure of ∠B :
∠B = (7x + 21)
∠B = 7 x 21 + 21
∠B = 168°
Hence, The measurement of ∠B is 168°
Learn more about Supplementary angles at:
brainly.com/question/13045673
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