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.
 
        
             
        
        
        
Answer:
Area = 25 square inches.
Step-by-step explanation:
Consider the large base triangle first. The height is 15 - 5 = 10
The base across is 10 (the length of the smaller stick).
The Area of that triangle is 1/2 * b * h 
Area = 1/2 * 10 * 10 = 50
Now the smaller triangle is the same base (the smaller stick of 10) * the height of 5
Area = 1/2  b * h
Area = 1/2  10 * 5
Area = 25
total area of the kite = 50 + 25 = 75