Suppose you add x liters of pure water to the 10 L of 25% acid solution. The new solution's volume is x + 10 L. Each L of pure water contributes no acid, while the starting solution contains 2.5 L of acid. So in the new solution, you end up with a concentration of (2.5 L)/(x + 10 L), and you want this concentration to be 10%. So we have

and so you would need to add 15 L of pure water to get the desired concentration of acid.
 
        
             
        
        
        
It would be (6,7) so which is why the Pokémon entered the facility
        
             
        
        
        
The answer is A. -2+5i.
First you set up the problem like this: (6+2i)-(8-3i)
Then you distribute the (-) into the second parenthesis. After doing that you should have something that looks like this: 6+2i-8+3i
Then you add like terms.
        
                    
             
        
        
        
The like terms are 16x and 2x