Question 885384
Ellipse Description.
2a=20 and {{{c=8}}}.
{{{a=20/2=10}}}.


Using the typical labeling for an ellipse, {{{b^2+c^2=a^2}}},
{{{b^2=a^2-c^2}}}
{{{b^2=10^2-8^2}}}
{{{b^2=100-64}}}
{{{b^2=36}}}.


You can plug-in everything into the standard form equation and solve for whichever coordinate you need:
{{{highlight(x^2/100+y^2/36=1)}}}