$A^\ast$ and $B^\ast$ are adjoint operators
This is a proof that is for an undergraduate linear algebra class. This is what I tried but I don't know if it is enough or rigorous enough.
$\langle Av, w\rangle = \langle w, A^\ast w\rangle$
$\langle ABv, w\rangle =\langle w, A^\ast B^\ast w\rangle$
$AB = BA$
then
$\langle BAv, w\rangle = \langle w, B^\ast A^\ast w\rangle$.
Hint: What is the adjoint of $ST$, for operators $S,T$?