The tableau above is an optimal tableau of a LP problem. If I want to find the optimal solution of dual, I know, I can rewrite this in terms of the original problem and remove the slack variables $x_4,x_5$ and then find the dual which is 2 dimensional which can be done by graphical methods.
But, how can we find the optimal solution of dual without doing all this? that is, by just looking at the tableau above?