The system of equations \frac{xy}{x + y} = 0, \quad \frac{xz}{x + z} = 0, \quad \frac{yz}{y + z} = 1 has exactly one solution. What is $z$ in this solution?
\(\frac{xy}{x + y} = 0, \quad \frac{xz}{x + z} = 0, \quad \frac{yz}{y + z} = 1 \)
x = 0
yz = y + z
zy - z = y
z ( y - 1) = y
z = y / (y - 1)
y z
2 2
z = 2
+1911 
