Find response of discrete time LTI system given input and impulse response
Note that the given definition of $x[n]$ is undefined for $n=0$. But even if you changed it by replacing the unit step $u[n]$ by the shifted step $u[n-1]$ to exclude the value $n=0$, then the problem would still be very hard to solve. So it's more than likely that the correct definition of $x[n]$ has no $n$ in the denominator, and the current form is just a consequence of a typo or of a misinterpretation.