I would say the answer is 35.
Answer:
a) For the first part we have a sample of n =10 and we want to find the degrees of freedom, and we can use the following formula:

d.9
b) 
a.15
c) For this case we have the sample size n = 25 and the sample variance is
, the standard error can founded with this formula:

Step-by-step explanation:
Part a
For the first part we have a sample of n =10 and we want to find the degrees of freedom, and we can use the following formula:

d.9
Part b
From a sample we know that n=41 and SS= 600, where SS represent the sum of quares given by:

And the sample variance for this case can be calculated from this formula:

a.15
Part c
For this case we have the sample size n = 25 and the sample variance is
, the standard error can founded with this formula:

you're absolutely correct.
each system is sold for $2150, that includes cost + markup, namely the markup is the surplus amount otherwise called "profit".
they sold 12 of those, 2150 * 12 = 25800
they had $4824.36 in profits from it, so if we subtract that from the sale price, we'll be left with the cost of all 12 systems
25800 - 4824.36 = 20975.64
that's the cost for all 12 systems sold, how many times does 12 go into 20975.64? 20975.64 ÷ 12 = 1747.97.
Answer:
2x² + 9x - 5
Step-by-step explanation:
Given
(2x - 1)(x + 5)
Each term in the second factor is multiplied by each term in the first factor, that is
2x(x + 5) - 1(x + 5) ← distribute both parenthesis
= 2x² + 10x - x - 5 ← collect like terms
= 2x² + 9x - 5