解:∵DE // BC
∴∠DEB = ∠EBC = 25°
∵ 在 △DEB 中
∴ ∠DEB + ∠DBE + ∠BDE = 180°
25° + 30° + ∠BDE = 180°
55° + ∠BDE = 180°
∠BDE = 180° - 55°
∠BDE = 125°
125