Consider the following premises. For all x_7, x_7 is not happy. There is at least one x_7 for which x_7 is a scientist if and only if x_7 is happy. For all x_7, x_7 is a scientist if and only if x_7 will drink water. Can we infer the following from them? There is at least one x_7 for which x_7 will not drink water.
 From the fact that there is at least one x_7 for which x_7 is a scientist if and only if x_7 is happy, and that for all x_7, x_7 is not happy we can infer that there is at least one x_7 for which x_7 is not a scientist. Finally, from the fact that for all x_7, x_7 is a scientist if and only if x_7 will drink water, and that there is at least one x_7 for which x_7 is not a scientist we can infer that there is at least one x_7 for which x_7 will not drink water. Therefore, the answer is yes.