Given: Triangle PQR with m∠P=(5x)° , m∠Q=(5x)° , and m∠R=(8x)° .
Prove: x = 10
By the triangle sum theorem, the sum of the angles in a triangle is 180°. Therefore, using the given and triangle sum_______theorem, . Using the substitution property, (5x)°+(5x)°+(8x)°=180° . Simplifying the equation gets 18x = 180. Finally, using the division property of equality ________ .