The number of students in a class is 75, out of which $$33\frac{1}{3}\%$$ are boys and the rest are girls. The average score in mathematics of the boys is $$66\frac{2}{3}\%$$ more than that of the girls. If the average score of all the students is 66, then the average score of the girls is:

The number of students in a class = 75
Number of boys = $$33\frac{1}{3}\%$$ of the total boys = 75/3 = 25
Number of girls = 75 - 25 = 50
Let the average score of girls be x.
Total score of girls = 50x
Average score of boys = x + 2x/3 = 5x/3
Total score of boys = 25 $$\times \frac{5x}{3}$$
Average score of all the students = 66
$$\frac{50x + 125x/3}{75}$$ = 66
$$\frac{150x + 125x}{75 \times 3}$$ = 66
x = 14850/275 = 54
So, the average score of the girls is 54.