SOLUTION: On Monday, 50% of the class is present. If only 30% of those who are absent is sick, what percent of the entire class are absent but not sick?
The fraction of those who are absent but not sick is 0.5*0.3 = 0.15 of the class population, or 15%.
The percentage of those who is absent but not sick is 50% - 15% = 35% of the entire class.