Hello,
[tex]\left{x = 4 \sin^2 \theta , \quad y = 3 \cos^2 \theta}\\\\
sin^2(\theta)= \dfrac{4}{x} , \quad cos^2(\theta)= \dfrac{3}{y} \\\\
sin^2(\theta)+cos^2(\theta)= \dfrac{4}{x} + \dfrac{3}{y} \\\\
\dfrac{3}{y}=1-\dfrac{4}{x}\\\\
y=\dfrac{3x}{x-4}
[/tex]
