In a class of 45 students it is know that 24 of them do Art 20 do chemistry and 22 do Biology. All the students do at least one of the three subjects. 3 do all the three subjects. Write 7 do Art and Biology 6 do Art and chemistry but not biology and 6 do chemistry and Biology. How many students do 1.Biology only 2.chemistry only 3.Art only 4.Two subject only