Răspuns :
a+b=12920
a-b=12900
a=12920-b
12920-b-b=12900
12920-12900=2b
2b=20
b=20:2=10
a=12920-10=12910
a-b=12900
a=12920-b
12920-b-b=12900
12920-12900=2b
2b=20
b=20:2=10
a=12920-10=12910
a+b=12920
a-b=12900
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2a=25820=>a=25820:2=>a=12910
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12910+b=12920=>b=12920-12910=>b=10
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Proba: 12910+10=12920
12920=1290
12910-10=12900
12900=12900
a-b=12900
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2a=25820=>a=25820:2=>a=12910
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12910+b=12920=>b=12920-12910=>b=10
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Proba: 12910+10=12920
12920=1290
12910-10=12900
12900=12900