I don't know where to start...

I have to use the strong duality theorem to prove that for any m x n matrix A and any m x 1 vector b, the system $\displaystyle Ax \leq b$ is unsolvable if and only if the system $\displaystyle y^TA = 0, y^Tb < 0, y \leq 0$ is solvable.

Please help

Nicole