Răspuns :
Adunam relatiile:
2a + b =79
2c + 3b= 99
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(+)
2a +4b + 2c= 178
Adunam relatia 2a +4b + 2c= 178 cu relatia 2a + b= 79.
2a + 4b + 2c = 178
2a + b = 79
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(+)
4a + 5b + 2c = 257