How do I factor the expressions 15a-13a, -6x - 18y, and 36abc+54ad?

2.12 school absences. data collected at elementary schools in dekalb county, ga suggest that each year roughly 25% of students miss exactly one day of school, 15% miss 2 days, and 28% miss 3 or more days due to sickness.61 (a) what is the probability that a student chosen at random doesn’t miss any days of school due to sickness this year? (b) what is the probability that a student chosen at random misses no more than one day? (c) what is the probability that a student chosen at random misses at least one day? (d) if a parent has two kids at a dekalb county elementary school, what is the probability that neither kid will miss any school? note any assumption you must make to answer this question. (e) if a parent has two kids at a dekalb county elementary school, what is the probability that both kids will miss some school, i. e. at least one day? note any assumption you make.