a) $ Xk[n]=d[n-k] $ -> syst. -> $ Yk[n]=(k+1)^2 d[n-(k+1)] $
To see if the system is time invariant we must run it through time delay.
$ Xk[n]=d[n-k] $ -> syst. -> $ Yk[n]=(k+1)^2 d[n-(k+1)] $ -> delay -> $ Zk[n] = Yk[n+n0] = (k+1)^2 d[n-(k+1)+n0] $
Alternately: $ Xk[n]=d[n-k] $ -> delay -> $ Yk[n]=d[n-k+no] $ -> syst. -> $ Zk[n]=(k+n0+1)^2 d[n-(k+no+1)+no] $
The outputs are not the same, therefore the system is not time invariant.
b) k would have to be 0 because only then is d[2n-(k+1)] not affected.
