p=29;alp=PrimitiveRoot[p]

a=5

bet=PowerMod[alp,a,p]

{y1,y}=PowerMod[{alp,bet},11,29]

m=6;y2=Mod[m*y ,p]

{y1,y2}

PowerMod[y1,-a,p]

Mod[y2*%,p]