A+B+C=6783
A+B=5714
B+C=4643
A=?, B=?, C=?
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inlocuim ecuatia a II a in prima si rezulta 5714+C=6783⇒C=6783-5714
⇒C=1069
B+C=4643⇒B+1069=4643⇒B=4643-1069
⇒B=3574
A+B=5714⇒A=5714-B⇒A=5714-3574
⇒A=2140
Verificare
A+B+C=6783
2140+3574+1069=6783
6783=6783