Question

Solve for x,y,z,
x+y=4
x+y+y+z+z+x=6
2x+2y+2z=6
x+y+z=3

Answer 1

x+y=4
x+y+z=3
4+z=3 as x+y=4
z=-1
Value of x and y cannot be determined as each given term leads us to the same term i.e. x+y=4
There should be one more term given to determine their values. Otherwise, according to this question, x and y have infinite number of values.
z=-1

Answer 2

x+y = 4

x+y+z = 3

4+z = 3

z = 3-4

z = -1

x+y = 4

Though we substitute the value of z in any equation, we can not determine the exact values of x and y.

There are infinite number of solutions for values of x and y.

So, in the equation,

x+y = 4

must be given other variable 'z'.

Hope it helps