ABCD=patrulater convex
A=3k
B=4k
C=5k
D=6k
Orice patrulater convex are 360 de grade
A+B+C+D=360 de grade
3k+4k+5k+6k=360 de grade
18k=360 de grade
k=360:18=20
k=20 de grade
A=3 x 20=60
B=4 x 20=80
C=5 x 20=100
D=6 x 20=120
Verificare=60+80+100+120=360 de grade