(х² - 10х + 21)/(2х² - 15х + 7) = ((х - 3)(х - 7)) /((2х - 1)(х - 7)) = (х - 3)/(2х - 1)
X - 4Y = 5
X = 4Y + 5
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15Y + 18Z = 33
18Z = 33 - 15Y
6Z = 11 - 5Y
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X + Y + 6Z = 4Y + 5 + Y + 11 - 5Y = 5Y - 5Y + 16 = 16
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X + Y + 6Z = 16