Data:
Principal: $600
Rate: 6% anually
Time: 120days
As the rate is anually you need to turn the 120days into years:
[tex]120\text{days}\cdot\frac{1\text{year}}{365\text{days}}=\frac{120}{365}\text{years}=\frac{24}{73}\text{years}[/tex]Multiply the principal, the rate (in decimals) and the time in years to find how much is the interest:
[tex]600\times0,06\times\frac{24}{73}=\frac{864}{73}=11.83[/tex]As she withdraws all the money add the principal and the interest to find how much she withdraws:
[tex]600+11.83=611.83[/tex]Then, rounded to the nearest dollar she withdraws $612