Lets draw another line XY || AB and CD.

According to the figure,

⇒ ∠a = 40° [Alternate angles]

⇒ ∠b = 35° [Alternate angles]

⸫ ∠x + ∠a + ∠b = 360° [Angle at a point = 360°]

⸫ ∠x = 360° - 40° - 35° = 285°