Given: ∠ADC = (3x + 5)° and ∠BDC = (2x – 25)°

Here AB is the straight line.

∴ ∠ADC and ∠BDC are linear pair.

⇒ ∠ADC + ∠BDC = 180°

⇒ 3x + 5 + 2x - 25 = 180°

⇒ 5x - 20 = 180°

⇒ 5x = 200°

⇒ x = 40°