a + b = 100
b + c = 110
a + c = 90
______________ → adun relatiile date
2 × a + 2 × b + 2 × c = 100 + 110 + 90
2 × ( a + b + c ) = 300
a + b + c = 300 : 2
a + b + c = 150 → suma celor trei numere
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150 - 110 = 40 ( a )
100 - 40 = 60 ( b )
110 - 60 = 50 ( c )
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