A is a vertical angle to 51 and is the same.
A = 51
C is a vertical angle to 53 and is the sane. c = 53
51 + c + d need to equal 180:
51 + 53 +d = 180
d + 104 = 180
d = 180-104
d = 76
d and b are vertical angles, so b = d = 76
a = 51
b = 76
c = 53
d = 76
