I really couldn't find the answer no matter how i tried Plz Help when I tried to solve it i got a really big numbers like a^6 ..etc' Okay what I did with this question is solving it by reducing the matrix to row echelon form, because that is the required way to solve it,but I didn't get any luck in that
You have the matrix approach in the post Amzoti mentions in his comment. So, let me try another, much less elegant, approach.
You have a system of three liner equations for three unknowns $x,y,z$. So, you can eliminate $x$ from the first equation, replace its expression in the second and third equations. Then now, eliminate $y$ from the second equation and replace its expression in the third equation which is jus linear in $z$. Solve it for $z$ and go backward and get $y$ and then $x$. The final result is $$x=-\frac{a^3+a^2}{a-2},y=\frac{a^2}{a-2},z= a$$ From here, you can have the same conclusions as in the previous post.