8 because 12-4=8. Im writing this part for the 20 characters
Answer:
5
Step-by-step explanation:
Remember, the rank of a matrix is the number of pivots or number of rows different of zero in the echelon form of the matrix.
Then, if A is a matrix
the maximum number of pivots that can have is one by row, that is, 5.
Then the maximum rank that A can have is 5.
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.
Answer:
-6/13
Step-by-step explanation: