Answer:
a) 
With:


b) 

c) 

d) 


Step-by-step explanation:
For this case we know the following propoertis for the random variable X

We select a sample size of n = 81
Part a
Since the sample size is large enough we can use the central limit distribution and the distribution for the sampel mean on this case would be:

With:


Part b
We want this probability:

We can use the z score formula given by:

And if we find the z score for 89 we got:


Part c

We can use the z score formula given by:

And if we find the z score for 75.65 we got:


Part d
We want this probability:

We find the z scores:



Answer:
12. -11
13. 2
Step-by-step explanation:
12. First recall the order of operations (BEDMAS): Brackets, Exponents, Division, Multiplication, Addition, Subtraction
For question 12 there is a division and its priority is before other operations in the equation so you must divide 16/-2 first which gives you -8.
From there because addition and subtraction is on the same level of order, you would do the question straight as it is shown (but replace 16/-2 with -8.
Your new equation is -10-8+7 = -11
13. follow the same as above using BEDMAS. It may help to look at it with additional brackets: ((-68)/(-4)) + ((5 x (-3))
- keep in mind there’s an addition between the two
Division and multiplication is on the same level in BEDMAS so first divide -68/-4 = 17
Second multiply 5 x -3 = -15
Now you can combine the two answers using addition: 17 + (-15) = 2
Answer:
Take the number of weeks as x
12x = 544 - 100
x =444/12
x = 37
Thus it would take her 37 weeks to buy her a laptop
$10.62? Im not sure if its correct