數學題-未知數

2x+y=8......(1)
y+3z=5......(2)
z+2w=1......(3)
5w+3x=9....(4)由(1) , y = 8 - 2x , 代入(2) :8 - 2x + 3z = 5
z = (2x - 3)/3 , 代入(3) :(2x - 3)/3 + 2w = 1
2x - 3 + 6w = 3
6w = 6 - 2x
w = 1 - x/3 , 代入(4) :5(1 - x/3) + 3x = 9
5(3 - x) + 9x = 27
4x + 15 = 27
x = 3 , y = 8 - 2x = 8 - 2*3 = 2z = (2x - 3)/3 = (2*3 - 3)/3 = 1w = 1 - x/3 = 1 - 3/3 = 0(x , y , z , w) = (3 , 2 , 1 , 0)

2x+y=8
y+3z=5
z+2w=1
5w+3x=9

2x=3+y=2=8
y=2+3z=1=5
z=1+2w=0=1
5w=0+3x=3=9

x=3 y=2 z=1 w=0