Okay, here we have this:
Considering the provided figure, we are going to find the requested coordinates after the given traslation, so we obtain the following:
So let's remember that to translate a point k units to the left we must subtract k from the x coordinate, we have:
J(-2, -8) -> J'(-2-8, -8)=J'(-10, -8)
K(6, -8) -> K'(6-8, -8)=K'(-2, -8)
L(-1, -6) -> L'(-1-8, -6)=L'(-9, -6)
Finally we obtain that the coordinates of the vertices are J'(-10, -8), K'(-2, -8) and L'(-9, -6).