Răspuns :
a+b+c=643
a+395=643=de aici il putem afla pe a
a=643-395
a=248
417+c=643
c=643-417
c=226
248+b+226=643-226
248+b=417-248
b=169
a+395=643=de aici il putem afla pe a
a=643-395
a=248
417+c=643
c=643-417
c=226
248+b+226=643-226
248+b=417-248
b=169
a+b=417 a+b+c=643 b+c=395 437+c=643 c=643-437 =206 b+206=395 b=395-206=189 a+189=417 a=417-189=228