Suppose there are 70 students in an examination with the students writing at least one of the subjects; Chemistry, Physics and Biology. Thirty(30) students offer Physics, 33 offer Chemistry and 40 offer biology, 10 students offer both Physics and Chemistry. Fourteen (14) of the students offer Physics and Biology, and 15 of them offer Biology and Chemistry. How many students offer only Biology

2 answers

are you familiar with Venn Diagrams? ... three intersecting circles?
Just to get you started, if x offer all three subjects, you have

(33+30+40)-(10+14+15)+x = 70