x =\frac{{KK}_{p}}{(1+{KK}_{p})} * {y}_{zad} + \frac{{K}_{p}}{(1+{KK}_{p})} * {u}_{b}   / *(1+{KK}_{p})

x*(1+{KK}_{p}) = {KK}_{p} * {y}_{zad} + {K}_{p} * {u}_{b} / : {K}_{p}

\frac{x*(1+{KK}_{p})}{{K}_{p}} = K * {y}_{zad} + {u}_{b}    / -(K * {y}_{zad})

{u}_{b} = \frac{x*(1+{KK}_{p}) - {KK}_{p}* {y}_{zad}} {{K}_{p}}

{u}_{b} = \frac{{y}_{zad}}{{K}_{p}}