Answer: A. (636.9, 653.1)
Step-by-step explanation:
Given : Sample size : n=56
Significance level :
Critical value :
Sample mean : 
Standard deviation : 
The 95% confidence interval for population mean is given by :-

Hence, 95% confidence interval for population mean is (636.9, 653.1).
Answer:
C. Add the equations
Step-by-step explanation:
Adding both the equations will help eliminating 5y.
It's a factor. This concept is widely used throughout algebra, and you'll probably bump into it through the end of high school and beyond.
A common use is expressing a term in <em>prime factorization</em>, or reducing a number to its most base parts- primes. For example:

Of course, a number like 13 which is already prime is made up of itself and 1. <em>Factors do not have to be primes.</em> 20 is also reducible through combinations of 1, 2, 4, 5, 10, and 20. Prime factorization is just a handy example.
Basically, factors multiply with each other to create other numbers, and numbers can be reduced down to their factors.
X = 6
<span>6+8x/2 = 30 if x = 6 and 5x = 30 if x =6</span>