Consider the following premises. For all x_7, x_7 is a cashier or x_7 is not a doctor. For all x_7, x_7 is not an artist. For all x_7, if x_7 were a cashier, then x_7 is a doctor. For all x_7, x_7 is an artist if and only if x_7 is a cashier. Can we infer the following from them? For all x_7, x_7 is not a doctor.
 From the fact that for all x_7, x_7 is a cashier or x_7 is not a doctor we can infer that for all x_7, if x_7 were a doctor, then x_7 is a cashier. From the fact that for all x_7, x_7 is an artist if and only if x_7 is a cashier, and that for all x_7, x_7 is not an artist we can infer that for all x_7, x_7 is not a cashier. From the fact that for all x_7, if x_7 were a doctor, then x_7 is a cashier, and that for all x_7, if x_7 were a cashier, then x_7 is a doctor we can infer that for all x_7, x_7 is a doctor if and only if x_7 is a cashier. Finally, from the fact that for all x_7, x_7 is a doctor if and only if x_7 is a cashier, and that for all x_7, x_7 is not a cashier we can infer that for all x_7, x_7 is not a doctor. Therefore, the answer is yes.