Question 166706
Let x  be the total amount of money invested.
given,one third invested in 9.75%
i.e.  x/ 3 amount invested in 9.75 %

rest of money= x - x /3 = x ( 1 - 1/3 )
                         =  x . 2/3 
                       2/3 x 

i.e. 2/3 x  of total amount invested in  11.5%

given total amount = $4912.50 

   Total amount  = principal + interest    ( SI = pnr/100 ) n= 18month = 3/2yrs

        4912.50 =  x  +  [ (x/3 * 3/2 * 9.75 )/100 + (2/3x * 3/2 *11.5)100]

                =  x +  0.39 x /8 +2.3x /20 (canceling common terms in each
term)

         4912.50 = 40 x + 1.95 x + 4.6x /40 ( taking LCM & Multiplying)
                 =46.55x /40
        4912.50 * 40 =46.55x
        196,500  =  46.55x

             x =  196500/46.55
               =  4221.27
Amount invested  = $4221.27