Consider the following premises. p_7 -> ~s. s. p_7 <-> w. Can we infer ~w from them?
 From p_7 -> ~s, s we can infer ~p_7. From p_7 <-> w we can infer w -> p_7. Finally, from w -> p_7, ~p_7 we can infer ~w. Therefore, the answer is yes.