Consider the following premises. q. w or ~q_6. q -> t_4. t_4 -> w. Can we infer w from them?
 From q -> t_4, t_4 -> w we can infer q -> w. From q we can infer q or q_6. From w or ~q_6 we can infer q_6 -> w. Finally, from q -> w, q_6 -> w, q or q_6 we can infer w. Therefore, the answer is yes.