x²/18+y²/30=1.
The distance c of either focus from the ellipse’s origin (at (0,0)) is given by:
c²=30-18=12, so c=√12=2√3.
Eccentricity, e=c/a where a is the length of the semi major axis, which in this case is √30. So e=2√3/√30=2/√10 or 2√10/10=√10/5=0.632 to the nearest thousandth.