Răspuns :
2a+3b+4c=85
5a+4b+3c=55
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a+b+c?
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3a+1b+1c=30
a+b+c=30:3 => a+b+c=10
2a+3b+4c=85. +
5a+4b+3c=55
7a+7b+7c =.140
7(a+b+c) =140
a+b+c=140÷7
a+b+c =20
2a+3b+4c=85
5a+4b+3c=55
---------------------
a+b+c?
----------------------
3a+1b+1c=30
a+b+c=30:3 => a+b+c=10
2a+3b+4c=85. +
5a+4b+3c=55
7a+7b+7c =.140
7(a+b+c) =140
a+b+c=140÷7
a+b+c =20