The answer is 8 days
Okay I don't know if you will understand my explanation is kind of complicated.
Maria earned 1 vacation day for every three months, so every 9 months she earned 3 vacation days.
A year has 12 months and two years have 24 months so let's suposse she worked this two years full time. 9x2= 18 that leaves 6 months left. So what we know is that she made two rounds of 9 months completely so that makes 6 days. So for the other 6 months which make 2 more days. Which leaves us 6+2=8 vacation days
