Well, if I'm reading this correctly, your first trapezoid has coordinates:
J(-2, 1), K(1, 1), L(3, -2), and then M(-4, -2).
Now it gives you the transition equation for how the trapezoid would move which is:
(x, y) -> (x + 5, y - 4)
Since you are looking for L, simply place L's coordinates inside:
L = (3 + 5, -2 - 4) -
Now solve it.
L = (8, -6) -
This should be the new set of coordinates for L.