Question

A triangle has vertices A(1,-3) B(7,5) and C(-3,5).L is the midpoint of side AC. Express CL as column vectors

Answer 1

L = (A+C)/2 = (-1,1)

Not sure what column vectors have to do with this, since we're just dealing with points.
But C+(L-C) = L
the directed segment CL is just L-C

Maybe you can work this into some kind of column vector setup.