Explicație pas cu pas:
1) Suma tuturor unghiurilor unui patrulater convex este de 360° => A+B+C+D = 360°
45°+63°+142°+D= 360°
D= 360°-250°
D=10°
2) A/1=B/2=C/3=D/4=K/1
A/1=K/1 => K=A
B/2=K/1 => 2K=B
C/3 =K/1 => 3K= C
D/4 =K/1 => 4K= D
A+B+C+D = 360°
K+2K+3K+4K = 360°
10K = 360 => K = 36
A=36
B= 72
C= 108
D= 144