Question 736818
"the major axis has a length of 12 million kilometers", means that {{{2*a=12}}} million kilometers.  


The eccentricity given means {{{c/a=1/5}}}, where c is the distance from either focus to the center of the ellipse.


Those two equations let you solve for the value of c.  Once you know a and c, you can find the value of b, the length of the semi-minor axis.  These have a pythagorean theorem relationship.


That should be enough for you to solve for the ellipse.  If you're unsure, a further bit of work can be shown.

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Just a few minutes doing a few steps gives me the result, {{{x^2/36+y^2/34.56=1}}}.  We use the relationship, {{{b^2=a^2-c^2}}}.