In ARST, mZR = (5x + 15)", mZS = (6x + 8)°, and mZT = (4x + 7)º.
What is the value of x?

Answer:
10
Step-by-step explanation:
(5x + 15)° + (6x + 8)° + (4x + 7)° = 180°
15x + 30 = 180 ⇒ x = 10