The hint is quite helpful; not overlapping is a good way of thinking about disjoint events. First of all, consider the first event. If one picks a trumpet that is free of defects, we have that the trumpet cannot have a dented bell. Similarly, if the trumpet has a dented bell, it cannot be free of defects; thus these events are disjoint since whenever one happens, we can be sure that the other does not. An example of non-disjoing events would be : 1) randomly picking a trumpet with a defect 2) randomly picking a trumpet with a dented bell. In this case, if the second event happens, we will have that the 1st event will also happen, so there is an overlap. A more generic example is the following: 1) randomly picking a tall person 2) randomly picking a brown-haired person. Since there are tall people with brown hair, there is overlap and thus the events are not disjoint.
