$\frac{x^2}{36} + \frac{y^2}{16} = 1$

$\frac{x^2}{36} + \frac{y^2}{20} = 1$

$\frac{x^2}{16} + \frac{y^2}{36} = 1$

$\frac{x^2}{20} + \frac{y^2}{36} = 1$