Answer:
D. 7n = 28
Step-by-step explanation:
Let's substitute 4 for n in each equation to check if it the resulting equation is correct:




Therefore the answer is D
 
        
                    
             
        
        
        
Remember property of exponents

add exponents of same base
ok so 
50,000 is 5 times 10^4
so
50000 times 10^15=
5 times 10^4 times 10^15=
5 times 

=
5 times 10^19
 
        
        
        
Answer:
x=(log(5/4))/(log(4))
Step-by-step explanation:
 
        
                    
             
        
        
        
Answer:
13
Step-by-step explanation: