The venn diagram above represents the students who were sick one day in january at a chicago high school. 80 students had only a fever, 60 students had only a cough, 90 students had only a headache, 10 students had only a cough and fever, 30 students had only a cough and a headache, 40 students had only a fever and a headache, and 20 students had a fever, cough, and headache. 100 students had other reasons for being absent that day. none of the sick students attended school that day. if 800 students attend the high school, how many students were at school that day?