Answer :
[tex]2y+5x-z=4y+6x\ \ \ \ \ \ |subtract\ 4y\ from\ both\ sides\\\\-2y+5x-z=6x\ \ \ \ \ |subtract\ 5x\ from\ both\ sides\\\\-2y-z=x\ \ \ \ \ \ |add\ z\ to\ both\ sides\\\\-2y=x+z\ \ \ \ \ \ |divide\ both\ sides\ by\ (-2)\\\\\boxed{y=-\frac{x+z}{2}}\\\\==============================\\\\8xy=z\ \ \ \ \ \ |divide\ both\ sides\ by\ 8x\\\\\boxed{y=\frac{z}{8x}}[/tex]
2y+5x-z=4y+6x
4y-2y=5x-6x-z
2y=-x-z
y=(-x-z)/2
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8xy=z
y=z/(8x)
4y-2y=5x-6x-z
2y=-x-z
y=(-x-z)/2
------------------------
8xy=z
y=z/(8x)