if i understand you correctly you are eventually trying to find what each variable equals and the way to do that with a system of equations is to find what each variable equals all with one variable in it such as finding what y equals in terms of x and what z equals in terms of x.

Then insert those equalities into one of the original questions and find what x truly equals.

then plug this number into your equalities for y and z and there you have it.

I hope this answers your question and truly helps