tentukan x,y dan z dari x+y+z=75,x-y-z=5,x-4y+z=0

x + y + z = 75
x - y - z = 5
x - 4y + z = 0

eliminasi?
x + y + z = 75
x - y - z = 5
___________ +
2x = 80
x = 40
40 - 4y + z = 0
40 + y + z = 75
____________ -
5y = 75
y = 15

x + y + z = 75
40 + 15 + z = 75
55 + z = 75
z = 20