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DAU COROANĂ
7a+14b+21=105 află 3a +6b


Răspuns :

7a+14b+21=105
7(a+2b)+21=105
7(a+2b)=105-21
7(a+2b)=84
a+2b=84/7
a+2b=12

3a+6b=2(a+2b)=2*12=24
7a+14b+21=105| :7=> a+2b=(105-21) :7=84:7=12| inmultim cu 3
=> 3a+6b=36
Succese!