How to solve following venn diagram question?

[champ0396]

There are 100 students in a class who give chemistry, physics and biology exam. 60 students fail in chemistry and 80 students failed in atleast one subject. 40 students failed in either chemistry or physics but not biology and 20 students passed in both chemistry and physics but not biology. Find number of students who passed only in chemistry.

[MathManTG6070]

Statement of problem#1) There are 100 students in a class who give chemistry, physics and biology exam. (#2) 60 students fail in chemistry (#3) 80 students failed in atl east one subject. (#4) 40 students failed in either chemistry or physics but not biology (#5) 20 students passed in both chemistry and physics but not biology.40 passed chemistry (#1, #2).20 of them passed physics and passed biology too (#3)20 of them passed physics and failed biology (#5)Since all 40 who passed chemistry also passed physics,NONE passed only chemistry.It's strange that we did not use item #4 at all.Usually, you need every piece of information givento solve the problem.=