I believe 8 is the answer 
        
                    
             
        
        
        
5.7y-5.2=y/2.5
Add 5.2 to both sides:
5.7y = y/2.5 + 5.2
y/2.5 = 0.4y
5.7y = 0.4y + 5.2
Subtract 0.4y from both sides:
5.3y = 5.2
Divide both sides by 5.3:
y = 5.2/5.3
y = 0.98113
 
        
                    
             
        
        
        
The answer is B
15 L of pure water must be mixed with 10 L of a 25% acid solution to reduce it to a 10% acid solution
        
                    
             
        
        
        
32/28 divide top and bottom by 4 =8/7
=1 1/7