=> ec. (1)... 15x+5y - 7x - y = 16 adica: 8x + 4y = 16 |:4 => 2x+ y =4 ;
ec. (2)... 3x - 9y - x+2y = - 12 adica: 2x -7y = -12 |*(-1) -2x+7y=12
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8y = 16
y = 2 ;
inlocuiesc y=2 in prima ecuatie ... 2x + 2 = 4 de unde x = (4-2):2 = 1 ;