La La la
Algebra
Level
3
\[ \begin{cases} (x+y+z)(x+y)=30\\ (x+y+z)(y+z)=18\\ (x+y+z)(z+x)=2 \end{cases} \]
Given that \(x, y\) and \( z\) satisfy the system of equations above, find the sum of all values of \(z\).
by
Department 8