Answer:

And if we want to find  we can use this formula from the definition of independent events :
 we can use this formula from the definition of independent events :

And the best option would be:

Step-by-step explanation:
For this case we have the following events A and B and we also have the probabilities for each one given:

And if we want to find  we can use this formula from the definition of independent events :
 we can use this formula from the definition of independent events :

And the best option would be:

 
        
             
        
        
        
0.4
4×1/10=0.4
multiply 4 by one-tenth
        
             
        
        
        
3 - 15  =  -12
so that is your answer