44. The unknown real numbers $x, y, z$ satisfy the equations
$$
\frac{x+y}{1+z}=\frac{1-z+z^{2}}{x^{2}-x y+y^{2}} ; \quad \frac{x-y}{3-z}=\frac{9+3 z+z^{2}}{x^{2}+x y+y^{2}} \text {. }
$$

F
Solution: $\sqrt[3]{14}$ Cross-multiplying in both equations, we get, respectively, $x^{3}+y^{3}=$ $1+z^{3}, x^{3}-y^{3}=27-z^{3}$. Now adding gives $2 x^{3}=28$, or $x=\sqrt[3]{14}$.