Answer:
7000 dollar, I guess.
Step-by-step explanation:
As we know the equation of simple interest is : I=Pnr
where I-interest
      P-principal or in this case the sum
      n- number of years
      r- rate perchantage
    as it asks for the sum, it should be:
     P= I/nr
      =3500 / 0.007 x 5 ( 7%= 0.007)
      = 10000
as she already invested 3000, so remains = (10000-3000)
                                    = 7000 dollar