Răspuns :
a+b+c=59
a+b=40
b+c=42
40+c=59
c=59-40
c=19
b+19=42
b=42-19
b=23
a+23=40
a=40-23
a=17
Verificare: 17+23+19=40+19=59
a+b=40
b+c=42
40+c=59
c=59-40
c=19
b+19=42
b=42-19
b=23
a+23=40
a=40-23
a=17
Verificare: 17+23+19=40+19=59