u=-5i+3j, v=-7i-6j, w=-3i+12j find (u)x(w)+(v)x(w)

We could still interpret this as a question about the cross-product of 3-d vectors.  Each of u, v and w lie in the x-y plane, so the cross-product result would point in the z-direction.

u=-5i+3j, v=-7i-6j, w=-3i+12j 

These are not 3-dimensional vectors, so this must be just a dot product problem.

u dot w = (-5*(-3)) + (3*12) = 15 + 36 = 51.

v dot w = (-7*(-3)) + (-6*12) = 21 - 72 = -51.

51 + (-51) = 0.

EDIT: Forgot to add, thanks Phill.