Question

x+y+z=4
2x+y+z=5
x-y+z=2

Answer 1

a) x+y+z = 4
b) 2x+y+z = 5
c) x-y+z = 2

a)x+y+z = 4
d)x = 4-y-z 

c) x-y+z = 2
     (4-y-z)-y+z = 2
4(-y-y)+(z-z) = 2
-2y = 2-4
-2y = -2
-y = -2/2

(-y = -1) (*-1)
y = 1

b) 2x+y+z = 5
2(4-y-z)+1+z = 5
(8-2-2z)+1+z = 5
8-2+1-2z+z = 5
7-z=5
-z=5-7
-z=-2

(-z=-2)*(-1)
z=2

d)x = 4-y-z 
x = 4-1-2
x = 1

a) x+y+z = 4
   1+1+2 = 4
   1+3=4
b) 2x+y+z = 5
   2*1+1+2 = 5
   2+1+2 = 5
   2+3 = 5
c) x-y+z = 2
   1-1+2=2
   0+2=2