Hi
Females: .55(.05 smoke)  and Males: .45 (.20smoke)
(a) Find the probability the student is a male smoker: P = (.45)(.20)
(b) Find the probability the student smokes.
 P = (.45)(.20) + (.55)(.05) = .1175
(c) If the student smokes, what is the probability the student is female?
   P(A|B) = P(A and B)/P(B)
     P(female|smoker) = (.55)(.05)/ .1175 = .0275/.1175 = .234
Wish You the Best in your Studies.