Case 1: Probabilities cannot add up to a number greater (or less) than 1. This would mean there is greater than a 100% chance of something happening which just doesn't make sense. 0.4 + 0.4 + 0.3 = 1,1
Case 2: You cannot have a negative probability. That is claiming that there is a -10% chance of an event happening, there is at the very least a 0%. Despite them "adding" up to 1, the negative probability makes no sense.
Hope I helped!
        
             
        
        
        
No its not am sure its not
        
                    
             
        
        
        
Well basically if they lost 8 points and gained 6, they have -2 points.
 
        
                    
             
        
        
        
Answer:
Step-by-step explanation:
x is the score she got on the fifth test.
Since her average score is 88, the sum of all five tests is 5×88. 
 x + 87 + 75 + 93 + 85 = 5×88 = 440
x = 440 -  87 - 75 - 93 - 85
x = 100
She got a 100 on her fifth test.