Your keyword here is "given." If we calculate the probability of an event, GIVEN that one event occurs, too, then we have dependent events, because the outcome of one event relies on the other. For this scenario, you have the probability of absence on any day of the week is 0.08, but then they say "well, but if it's Friday, that probability actually goes up quite a bit." This tells you that your events aren't independent because the day being Friday increases the chances of a student being absent from the baseline 0.08 probability.
