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abc = ?
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abc : 15
b+ c= 10
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Obs. abc : 15, abc : 3 , ( a+ b+ c) : 3
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abc : 5 , c ∈ { 0; 5 }
s₁. c= 0, b+c = 10
b+ 0 = 10
b = 10-0
b = 10 , imp. , b= cifră
s₂: c = 5 b+c = 10 ( a+ b+ c) :3
b+ 5 = 10 a+ 5+5 : 3
b = 10-5 a+ 10 : 3 , a ∈ { 2; 5; 8}
b = 5
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s.finală: abc ∈ { 255; 555; 855}
