Besar sudut BEC adalah...

ABC = 180 - 102 = 78
BCE = 180 -148 = 32
BEC = 180- (78+32) = 70

Sudut ABE + Sudut CBE = 180
102 + Sudut CBE = 180
Sudut CBE = 78
Sudut CBE + Sudut BEC = Sudut DCE
78 + Sudut BEC = 148
Sudut BEC = 70°