Answer:
22.5°
Step-by-step explanation:
We know that the measure of straight line is 180° . Therefore the sum of all angles will be 180° .
⇒ 90° + x + 3x = 180°
⇒ 90° + 4x = 180°
⇒ 4x = 90°
⇒ x = 90°/4
⇒ x = 22.5°
