Răspuns:
1) Adunam ecuatiile 2 si 3:
b + c = 5
a + c = 22
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( a + b ) + 2c = 22 + 5 si inlocuim a+ b = 21
21 + 2c = 27
2c = 27 - 21
2c = 6
c = 6 : 2
c = 3
a + c = 22
a + 3 = 22
a = 22 -3
a = 19
b + c = 5
b + 3 = 5
b = 5 - 3
b = 2
a x b x c = 19 x 2 x 3 = 38 x 3 = 114
a x b x c = 114