Given the following system:

notice that we can easily solve for z on the third equation to get the following:

doing the substitution on the first equations we get:

Now, notice that on both equations we get 11y and -11 y, then we can add both of them to find the value of x:

we have that x=3, now we can find y by using this value on one of the previous equations:

finally, for z we have:

therefore, the solution of the system is (x,y,z)=(3,-2,-4)