5 / 3 is improper fraction. To change it into mixed fraction you have to divide 5 by 3. i.e. 1 is the quotient, 3 is the divisor, 5 is the dividend, and 2 is the reminder.
To write it in the mixed fraction you will only need the quotient, remainder and divisor. First you will write quotient in the middle then the remainder divided by divisor i.e.1 2/3 where 1 is quotient, 2 is remainder and 3 is divisor.
If the solutions are x=-4 and x=3, then it must have factors (x+4)(x-3). Assuming there is no GCF or leading coefficient other than 1, multiply with FOIL to find the standard form.