Two angles lie along a straight line. If m∠A is five times the sum of m∠B plus 7.2°, what is m∠B?

Given:
m∠A = 5 × (m∠B + 7.2°)
To find:
The measure of m∠B
Solution:
m∠A = 5(m∠B + 7.2°)
Sum of adjacent angles in a straight line = 180°
m∠A + m∠B = 180°
5 × (m∠B + 7.2°) + m∠B = 180°
5 m∠B + 36° + m∠B = 180°
6 m∠B + 36° = 180°
Subtract 36° from both sides.
6 m∠B + 36° - 36° = 180° - 36°
6 m∠B = 144°
Divide by 6 on both sides, we get
m∠B = 24°
The measure of ∠B is 24°.
The angle of m∠B should be 24 degrees when the m∠A is five times the sum of m∠B plus 7.2°.
Since
m∠A = 5 × (m∠B + 7.2°)
So,
m∠A = 5(m∠B + 7.2°)
Also we know that
Sum of adjacent angles in a straight line = 180°
Now
m∠A + m∠B = 180°
5 × (m∠B + 7.2°) + m∠B = 180°
5 m∠B + 36° + m∠B = 180°
6 m∠B + 36° = 180°
6 m∠B = 144°
m∠B = 24°
Hence, The measure of ∠B is 24°.
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