The statement to remember here is that: The sum of angle measures on a straight line add up to 180°
Form an equation for the sum of angle measures as;
12x + 19 + 22x - 9 = 180°
Collect like terms
12x + 22 x + 19-9 =180°
34 x + 10 = 180°
34x = 180° - 10°
34 x = 170°
x = 170° /34
x = 5°
Answer
x = 5°