Question 1186892
Here's how to solve this problem using conditional probability:

Let's define the events:

*   E: The subject has been exposed to the allergen.
*   R: The subject experiences a reaction to the allergen.

We are given the following probabilities:

*   P(E ∩ R) = 0.60 (Probability of exposure *and* reaction)
*   P(R|E) = 0.80 (Probability of reaction *given* exposure)

We want to find P(E), the probability that a subject has been exposed to the allergen.

We can use the formula for conditional probability:

P(R|E) = P(E ∩ R) / P(E)

Rearranging this formula to solve for P(E), we get:

P(E) = P(E ∩ R) / P(R|E)

Now, plug in the given values:

P(E) = 0.60 / 0.80
P(E) = 0.75

Therefore, the probability that a randomly selected subject will have been exposed to the allergen is 0.75, or 75%.