"their threads make equal right angles" can only refer to the threads on the worm gear as the drive gear and the threads on the driven gear, since only worm gears can engage at right angles. It seems a misnomer to mear to call a worm gear a "gear" because we un-initiated laymen associate the name of "gear" with the shape of a tooothed spur gear.
Diana, be aware they also give you problems that cannot be solved or are plain nonsense. (Maybe to train you for the fact of your future engineering environment, like people with authority over you talking nonsense, or to fine-tune your sense of awareness in general, and so on). First, determine for yourself "whether" the question makes any sense, then "how" it makes any sense. Invest your mental resources and time wisely by first answering all the easy questions. Then you go to the time-consuming questions, further distinguishing which will be the easiest to answer. In the meantime, by answering the easy questions first, you may discover the answers to the easy questions are part of the answer to the complex questions. The easy question put you in the right frame of mind, but the sequence of questions is not from easy to complex. So, answering questions in the sequence they are being asked will surely put you at a disadvantage to the person who looks over all the questions first before answering the first one. Your objective is to pass the test. Always ask yourself: what is my outcome, what do I want to achieve, before starting any effort.