I need to prove $[L_i,R_j] = i\hbar\epsilon_{ijk}R_{k}$.
I have that $L_i = \epsilon_{ijk}R_{j}P_{k}$ , so the commutator becomes:
$$[\epsilon_{ijk}R_{j}P_{k},R_{j}] = \epsilon_{ijk}\left(R_j[P_k,R_j]+[R_j,R_j]P_k\right).$$
I know $[R_j,R_j] = 0$ but I'm unsure about the other commutator.