a=b+c=172
d=cxi+r
a=2b+6
b=3c+12
a=2x(3c+12)+6
a=6c+24+6
a=6c+30
c _____/
b _____/_____/_____/.......12....../
a _____/_____/_____/_____/_____/_____/.............30................./
172-12-30=130 cele 10 seg egale in total
130:10=13 fiecare seg egal
a=13x6+30=
b=13x2+6=
c=13