Simple interest is computed using ...
... I = Prt . . . . . where P is the principal amount, r is the interest rate, and t is the lenght of time
The balance in the account is the principal plus the interest:
... P + I = P(1 + rt)
That balance is $2500, so we have
... $2500 = P(1 + 0.054·6) = 1.324P
... $2500/1.324 = P ≈ $1,888.22
The amount that must be deposited now is $1,888.22 in order for the balance to be $2,500 in 6 years.