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We present new radial velocities and UBV photometric observations of three eclipsing binaries, V799 Cas, BX Psc and HD172189, in order to increase the number of close binaries with absolute parameters determined accurately. Standard wide-band indices for the systems and comparison stars were determined accurately. Using the times of mid-eclipses, new ephemerides are calculated for three systems. V799 Cas and HD172189 consist of two well-detached components in eccentric orbits. BX Psc is a single-lined eclipsing binary which consists of a late-A and an early-K star. The effective temperatures of the hotter components and reddening of the systems have been estimated from Johnson wide-band UBV photometric calibrations. The UBV photometric data and radial velocities were analysed simultaneously for the systems' parameters using Wilson-Devinney code. The masses have been found to be 3.08±0.40, 2.97 ±0.40; 1.85±0.14, 0.80±0.08; 2.06±0.15, 1.87±0.14 M_☉ for the primary and secondary stars of V799 Cas, BX Psc and HD172189, respectively. The radii of the components are derived in the case of V799 Cas: 3.23±0.14, 3.20±0.14; in those of BX Psc: 3.76±0.14, 2.18±0.09; and HD172189: 4.01 ±0.09, 2.97±0.07 R_☉. We have calculated the distances to the systems of V799 Cas, BX Psc and HD172189 as 607±35, 213±6 and 432±12 pc, respectively, using bolometric magnitudes and empirical bolometric corrections for the component stars. The model predictions match the measured properties of V779Cas, BX Psc and HD172189 for an age of 250 Myr, 1 Gyr and 890 Myr, respectively. A subsolar fractional metal abundance, Z ~ 0.008, provides a better match to the absolute parameters of all three systems.