Micellar solution of ternary systems of nonionic/ionic (TritonX-100/1-bromo-4-tridecylpyridine) surfactants in water were studied by small-angle neutron scattering. Formation of mixed micelles was detected. It was found that system behavior versus temperature is strongly dependent on the ratio between surfactant concentrations. Aggregation number and surface charge of micelles were calculated using the rescaled mean spherical approximation.