A method of calculating cascades with several additional external flows that generalizes the known methods is proposed. The efficacy of the proposed method was tested on the calculated concentration of 183W in the additional product flow. Also considered is feeding into the cascade regenerated fuel from light water reactors, uranium obtained from spent fuel from industrial reactors, and depleted uranium for their enrichment to the required concentration of 235U in the product flow. For the example of separating a mixture of xenon isotopes, it is shown that two target components can be concentrated simultaneously in a cascade with two additional product flows.