Answer:
0.1356
Explanation:
This is a probability exercise. Let's define some probability concepts. 
Given two events A and B :
(A∩B) = (A,B) 
(A,B) is the intersection event where A and B occur both at the same time.
We define  as the conditional probability '' The probability of the event A given that we know that the event B occurred'' as :
 as the conditional probability '' The probability of the event A given that we know that the event B occurred'' as :

Where 
Now, if A is an event and  is its complement ⇒
 is its complement ⇒ 

Finally we define the probability of the union between two events A and B :
P(A∪B) = P(A) + P(B) - P(A,B)
If the events A and B are independent between them ⇒ P(A,B) = 0 ⇒
P(A∪B) = P(A) + P(B) 
Let's define the following events for this exercise : 
D : ''People taking this test that have the disease'' 



P : ''The test is positive'' 



And 
We are looking the probability of 
P(P') = P [(P'∩D) ∪ (P'∩D')] 
Given that this events are independent between them : 
 (I)
 (I)
Let's write the conditionals for this problem : 
 ⇒
 ⇒

 (II)
 (II)
And the another conditional : 
 ⇒
 ⇒

 (III)
 (III)
Replacing (II) and (III) in (I) : 


We find that the probability of the test indicating that the person does not have the disease ( P(P') ) is 0.1356