Firstly you have to reduce the 4 variables to a double system of equation with only 2 variables.
Let's say, first we have to eliminate Z:
Take 1st & 3rd equation & multiply each term of the 1st by (- 1). One done you add up the 1st & the 3rd & you will get:
5W - 4x + 2y = - 18
Follow the same methodology to find another equation without z. Once done you will have a system of 2 equation with 2 variable easy to solve,
At the end you will find:
w = -3
x = -2
y = -1
z = 3
