Q1: y = x/2 - 2/3
6y = 3x - 4
-3x + 6y = -4
This is equivalent to 3x - 6y = 4, so the two lines coincide. All real numbers don't work on this system. The solution is {(x, y): 3x - 6y = 4}, or all points on the line with equation 3x - 6y = 4. This is NOT the same as all real numbers.

Q2: This system is dependent, with z = 0 and x - 2y = 0, so there are infinitely many solutions, all in the form x = 2t, y = t, z = 0.

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