B. 90°

C. 45°

D. 40°

• Given: Line m || line n and line p is a transversal

• To find: The value of x.

Now in the given figure we have 3x and x. 3x and x form a pair of interior angle.

Now by the property of interior angels we know that, each pair of interior angles formed by two parallel lines and their transversal is of supplementary angles i.e. 180°.

∴ x+3x=180(∵ Property of interior angles.)

⇒ 4x=180

⇒

∴ The value of x is 45°.