Answer:

And replacing we got:

And then the estimator for the standard error is given by:

Step-by-step explanation:
For this case we have the following dataset given:
20.05, 20.56, 20.72, and 20.43
We can assume that the distribution for the sample mean is given by:

And the standard error for this case would be:

And we can estimate the deviation with the sample deviation:

And replacing we got:

And then the estimator for the standard error is given by:

First we expand the brackets:
-2a + 8 + 6a = 36
4a + 8 = 36
We then need to get the a's onto one side and the numbers onto the other:
4a = 28
We can then divide to get an x by itself:
a = 28/4 = 7
Answer:
The solution is (0, 3)
Step-by-step explanation:
First, reduce 2x + 4y = 12 to x + 2y = 6, for easier calculations.
Next, substitute y - 3 for x in the other equation:
y - 3 + 2y = 6, or
3y = 9
Then y = 3. Since x = y - 3 in general, x = 3 - 3 = 0 when y = 3.
The solution is (0, 3)
Can you please include a pic