I am assuming you are trying to write seven to the power of fourteen and seven to the power of two, and if that is what you meant the correct answer is 13841287201.
        
             
        
        
        
(4*2)-(2*-3)+(5*5)= 8-6+25= 27
        
             
        
        
        
Let's say that the value invested in the account with a rate of 8% is "x", then the amount invested in the account with a rate of 12% is:

To calculate the total interest we need to calculate the interest of each individual account and sum them:

The total interest is the sum of the two expressions above:

The value invested in the account with 8% interest is 830, the one invested in the account with 12% interest is 1280.