Consider the following premises. For all x_3, x_3 will cook. There is at least one x_3 for which x_3 is not a scientist. For all x_3, x_3 will not cook or x_3 is a taxi driver. Can we infer the following from them? There is at least one x_3 for which x_3 is a taxi driver.
 From the fact that for all x_3, x_3 will cook we can infer that for all x_3, x_3 will cook or x_3 is a scientist. From the fact that for all x_3, x_3 will cook or x_3 is a scientist, and that for all x_3, x_3 will not cook or x_3 is a taxi driver we can infer that for all x_3, x_3 is a scientist or x_3 is a taxi driver. Finally, from the fact that for all x_3, x_3 is a scientist or x_3 is a taxi driver, and that there is at least one x_3 for which x_3 is not a scientist we can infer that there is at least one x_3 for which x_3 is a taxi driver. Therefore, the answer is yes.