Answer:
90°
Step-by-step explanation:
AB and CD are parallel lines and EF is reversal
Therefore angles BGH and DHG are consecutive interior angles
As we know the sum of consecutive interior angles equals to 180°:
∠BGH + ∠DHG = 180°
Line GP bisects angle BGH , therefore
m∠PGH = 1/2*m∠BGH
Line HP bisects angle GHD, therefore
m∠PHG = 1/2*m∠GHD
Sum of two angles of triangle GHP:
m∠PGH + m∠GHD = 1/2(∠BGH + ∠DHG) = 1/2*180° = 90°
Therefore the missing angle a is:
∠a = 180° - (m∠PGH + m∠GHD) = 180° - 90° = 90°
