Given {x + 4y-3z = 0,4x-5y + 2Z = 0, then 3y-5z of 2x-y + 3Z =?

Given {x + 4y-3z = 0,4x-5y + 2Z = 0, then 3y-5z of 2x-y + 3Z =?

(1) 5 + (2) × 4
21x-7z=0
∴z=3x
Substituting z = 3x into (1) yields
x+4y-9x=0
∴y=2x
Substituting y = 2x, z = 3x into the original formula, we get
Original formula = (6x-15x) / (2x-2x + 9x) = - 9x / 9x = - 1