Here's the solution,
the opposite angles of parallelogram are equal, so, Angle G = Angle E
=》3x + 11 = 5x - 9
=》5x - 3x = 11 + 9
=》2x = 20
=》x = 10
value of x = 10
now, Angle G = 5x - 9
=》(5 × 10) - 9
=》50 - 9
=》41°
Angle G and Angle F are supplementary, so
=》 41° + Angle F = 180°
=》Angle F = 180° - 41°
=》Angle F = 139°