The value of angle a,b,c and d would be = 81°,18°,81° and 18° respectively.
How to calculate the missing angles of the quadrilateral?
To calculate the value of the missing angles, the following steps should be taken as follows:
From ∆WXY,a+b = 180-60+39
= 180-99= 81°
From ∆ZYX, d+c = 180-24+57
= 180-81 = 99
From bisector of the angle of parallelogram,
c = 99-81 = 18°
D = 99-18 =81°
a = 81°
b = 18°