The possibility of calculating the thermodynamic properties of melts in the Na₂O-B₂O₃-SiO₂ system (as in the previously studied Cs₂O-B₂O₃-SiO₂ system) formed by two glass-former oxides (B₂O₃, SiO ₂) and one modifier oxide (Na₂O) with the use of the vacancy variant of the generalized lattice theory of associated solutions is demonstrated. A comparison with the experimental thermodynamic functions previously determined by the electromotive force method and high-temperature mass spectrometry at temperatures of 1200, 1273, and 1350 K shows that the calculations performed within this approach lead to reliable thermodynamic functions. It is noted that the proposed model ignores the change in the coordination number of boron atoms to four and the possibility of forming associates in melts of compositions lying in the metastable phase separation region at temperatures higher than the phase separation temperature.