Eliza has now on her account $ 487 + ( $15+77,49 + 124,28) = $ 703,77 and this is the last amount M
NOW M = C + I, where, M is the final amount, C is the initial capital and I is the interest, of this formula obtain the I, WHERE I = M-C , I = $ 703,77 - 324,18 = 379,59
NOW I = C *i*n, WHERE, i , is the rate of interest, n is the time between the dates, ( 29 -19 = 11 days ), and with the formula you obtain i = I / C*n, i = 379,59/ ( 324,18* 11) = 0.1
then you must calculate the initial capital deposited in her account is calculated with
C = M / 1+(i*n) , C = 703,77/ 1 + (0,1*11) , 703,77/ 2.1 = $335,12