If you plot J and K in a coordinate plane, you see that the line formed is a perfectly horizontal line through y = 2. In order for this triangle to be an isosceles, the third x-coordinate would have to be located midway through the x-coordinates of the base. The midpoint between the x-coordinates is found by adding the 2 x-coordinates and dividing the sum by 2. -6+\3 = -3 and -3/2 = -3/2. So the x-coordinate is -3.2 or -1.5
The third vertex of an isosceles triangle is on the perpendicular bisector of the base. Here, the base is on the horizontal line y=2, so the perpendicular bisector will be on the vertical line with the x-value the same as the midpoint of the base.
