The ratio of coordinates in the image to the coordinates of the original will tell you the dilation factor when diation is about the origin (as here).
Jx'/Jx = -2/-3 = 2/3
This same ratio is true for the other 5 coordinate values, so we know that ...
... the scale factor used in the dilation is 2/3.
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Jy'/Jy = -8/-12 = 2/3
Kx'/Kx = -4/-6 = 2/3
Ky'/Ky = -10/-15 = 2/3
Lx'/Lx = -6/-9 = 2/3
Ly'/Ly = -8/-12 = 2/3
