How far apart are the foci of an ellipse with a major axis of 20 feet and a minor axis of 14 feet?

The lenngth of the major axis / 2  = a = 10     ...the length of the minor axis/ 2  = b  = 7

The focal length, c, is given by : √[ a^2 - b^2 ] = √[ 10^2 - 7^2 ]  = √51 units......and the distance between the focal points  = 2c  = 2√51 ≈ 14.28  units