Let, amount of 14% solution required is x ounces.
So, amount of 8% solution will be ( 28 - x ) ounces.
Now, mathematical equation is :

Therefore, amount of 14% solution and 8% solution required is 4 ounces and 24 ounces respectively.
Hence, this is the required solution.
81 by 9 means 81 times 9 ( or 81 x 9). The answer however would be 729