Answer:
The sum of the age of pupils is 81
Step-by-step explanation:
Let sum of age of 18pupils = x
Average ages = 4.5
Average = total/no. of pupil
4.5 = x/18
x = 81
Answer:
Kevin can afford to have 15 guests at his party.
Step-by-step explanation:
You know that Kevin's party costs $52, so you can subtract 52 from 97, which is 45. So, he can spend $45 dollars on guests. $45 divided by 3, the amount it takes for each guest, to get 15.
If an expression is the difference of two squares, it will follow this format:

where a and b are integers or variables.
1)

Since the expression follows the format, it's a DoTS.
2) Since the binomial has an addition sign, it isn't a DoTS.
3)

The second term isn't an integer, so the expression isn't a DoTS.
4)

Since the expression follows the format, it's a DoTS.
Therefore, the first and fourth expressions are differences of two squares.
Answer:
If the circle shown (which I can't see) has a radius of 2, then it's equation 3, if the radius is 4, then it's equation 4.
Step-by-step explanation:
The equation for a circle is 
Where (h, k) is the center and r is the radius.
Answer:
Right tailed tests
Step-by-step explanation:
When dealing with the chi-square goodness-of-fit test, we are trying to find out if the sample in question comes from the population with the claimed distribution.
Now, the idea behind this concept is that if the observed value is very close to the expected/claimed value, it means the square of the deviations will now be small. The weighted square deviations will now be calculated and if their sum is small, it means the observed values will be close to the expected values and there would thus be no reason to reject the claim that it came from the distribution. Thus, it's only when the sum is large, that there would be a reason for questioning the distribution.
Thus, goodness of fit tests are always right tailed tests.