Answer: D. 10
Explanation:
As a basic concept, we are aware that the angle created on a straight line is equal to 180°.
One angle measures 30 degrees while the other measures 15x degrees.
To ensure that the angles add up to 180°, it is necessary to include both angles.
∴ 30° + 15x° = 180°
15x° = 180°- 30°
15x° = 150°
x° = 150°/15
∴ x° = 10
Proof: 30°+ 15×10° = 180°
30° + 150° = 180°
180° = 180°