a + b = 84
b + c = 64
a + c = 34
____________ → adun sumele
2 × a + 2 × b + 2 × c = 84 + 64 + 34
2 × ( a + b + c ) = 182
a + b + c = 182 : 2
a + b + c = 91 → suma celor trei numere
______________________________
91 - 64 = 27 ( a ) → primul numar
84 - 27 = 57 ( b ) → al doilea nr.
64 - 57 = 7 ( c ) → al treilea nr.
________________________