Question 166704
Amount borrowed  = $6000

if she borrowed 'x' at 15.5% , rest is 6000 - x and borrowed at 14.25%

simple interest = p*n*r / 100     n = 3yrs + 6m = 3+ 1/2 yrs = 7/2 yrs

    3150  = x * 7/2 * 15.5 /100 + (6000 - x ) * 7/2 * 14.25 /100 
         = 0.5425 x + (6000 -x) *0.4988
         = 0.5425x + 6000 *0.4988 -0.4988x
         =  0.0437 x + 2992.8
3150 -2992.8 =  0.0437 x
 157.2 =0.0437x
  x  = 157.2/0.0437  = 3597.25

Amount she borrowed at 15.5% = $ 3597.25 

Amount she borrowed at 14.25 % =  6000 - 3597.25 
                               =  $ 2402.75