Answer:
x = 90
Step-by-step explanation:
The 90-degree angle and "x" form a straight line. The degree measurement of a straight line is 180. That means that if one adds 90 and "x", they will get 180, and therefore, x equals 90.
18 ÷ 3 = 6
21 ÷ 3 = 7
Answer: 6/7
The applicable theorem is the one that tells you the exterior angle is equal to the sum of the opposite interior angles.
9x = (5x) +(9 +x)
9x = 6x +9 . . . . . . . . collect terms
3x = 9 . . . . . . . . . . . . subtract 6x
x = 3 . . . . . . . . . . . . . divide by 3
The value of x is 3.
_____
The angles (clockwise from left) are then
(9*3)° = 27°
(5*3)° = 15°
(9 +3)° = 12°
This is an obtuse triangle, obviously not drawn to scale.