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2014-10-07T16:00:45+03:00
Cel mai inteligent răspuns!
2014-10-07T16:14:12+03:00
7a+9b+9c+7d=7(a+d)+9(b+c)
b+c=30-(a+d)=20
7(a+d)+9(b+c)=7x10+9x20=70+180=250
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