Consider the following premises. For all x_7, if x_7 drives a car, then x_7 is climbing a mountain. For all x_7, x_7 will write a letter or x_7 will drive a car. For all x_7, x_7 will write a letter if and only if x_7 will read a book. For all x_7, if x_7 reads a book, then x_7 is climbing a mountain. Can we infer the following from them? There is at least one x_7 for which x_7 will not climb a mountain.
 From the fact that for all x_7, x_7 will write a letter if and only if x_7 will read a book we can infer that for all x_7, if x_7 writes a letter, then x_7 is reading a book. From the fact that for all x_7, if x_7 writes a letter, then x_7 is reading a book, and that for all x_7, if x_7 reads a book, then x_7 is climbing a mountain we can infer that for all x_7, if x_7 writes a letter, then x_7 is climbing a mountain. Finally, from the fact that for all x_7, if x_7 writes a letter, then x_7 is climbing a mountain, that for all x_7, if x_7 drives a car, then x_7 is climbing a mountain, and that for all x_7, x_7 will write a letter or x_7 will drive a car we can infer that for all x_7, x_7 will climb a mountain, which contradicts that There is at least one x_7 for which x_7 will not climb a mountain. Therefore, the answer is no.