Answer:
1. m∠P + m∠Q + m∠R = 180°
2. x = 10
Explanation:
By the triangle sum theorem, the sum of the angles in a triangle is 180°. Therefore, using the given sum theorem, m∠P + m∠Q + m∠R = 180°. Using the substitution property, (5x)° + (5x)° + (8x)° = 180°. Simplifying the equation gets 18x = 180°. Finally, using the division property of equality, x = 10.
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