Answer:
21, 9
Step-by-step explanation:
If girls are x, then boys are x + 12
x + x + 12 = 30
2x + 12 = 30
2x = 18
x = 9
There are 9 girls and 21 boys
The fraction 8/21 cannot be simplified because the numerator and denominator don't have a common factor except 1.
Answer:
Step-by-step explanation:
Given that a professor sets a standard examination at the end of each semester for all sections of a course. The variance of the scores on this test is typically very close to 300.

(Two tailed test for variance )
Sample variance =480
We can use chi square test for testing of hypothesis
Test statistic = 
p value = 0.0100
Since p <0.05 our significance level, we reject H0.
The sample variance cannot be claimed as equal to 300.