The present notebook shows how one can compute Vapour-Liquid-Liquid Equilibrium data using the two-parameter Margules model. This method is applied to a ternary system: water-ethanol-ethyl acetate. In addition, we show how one can derive the expressions of the activity coefficients from the excess molar Gibbs function. Results are in qualitative agreement with Figure 6 in the paper by Pham and Doherty, Chem. Eng. Sci., Vol 45, N° 7, pp 1823-1836, 1990. In the figure presented in the notebook, the author shows the tie lines as well as the vapour line. Boiling temperatures are also given.