James B. answered • 06/09/16

Experienced, Patient, Passionate ISEE Math Tutor

A = 267 People

B = 253 People

Neither = 40

A ∩ B = 410 - 267 =

The number of people that tested positive for virus A & B, is

A ∩ B = A + B - (450 - 40)

= 267 + 253 - 410

= 110

The number of people that tested positive for A only is

267 - 110

= 157

The probability of a random patient testing positive for A only is

157/450

The probability of a random patient testing positive for A given they tested positive for B is:

110/253

110/253