I'm not going to do it for you.  It's too long,
I just tell you how.

Line up the letters and symbols:

(1)  w +  x -  y +  z = 0
(2)  w - 2x - 2y -  z = 5
(3)  w - 3x -  y +  z = 4
(4) 2w -  x -  y + 3z = 7

The idea is to reduce that down to a system of 4 equations and 4 unknowns to a
system of 3 equations and 3 unknowns.
Then we'll reduce that system down to a system of 2 equations and 2 unknowns,
and then finally to just 1 equation and just 1 unknown, which everybody knows
how to solve and get a number, because that's basic algebrs.  Then you plug
that back in to one of the equations in two unknowns and solve for that
remaining unknown.  Then plug those two  back in one of the equations with 3
unknowns and solve for that remaining unknown. and so on until you have all
the unknowns.

Eliminate z from (1) and (2) and get

(5)  2w -  x - 3y = 5

Eliminate z from (2) and (3) and get

(6)  2w - 5x - 3y = 9

Eliminate z from (3) and (4) and get

(7)  -w + 8x + 2y = -5

Now you have a system of 3 equations in 3 unknowns:
 
(5)  2w -  x - 3y =  5
(6)  2w - 5x - 3y =  9
(7)  -w + 8x + 2y = -5

Now eliminate a letter from two pairs of those, etc., and get 2 equations
in 2 unknowns. etc., etc.,

When you get it down to 1 equation and 1 unknown, you solve that and \
substitue back to get the next unknown, etc.

Edwin