Can you please explain why these are the answers for these questions

7. X\"N(100, 5). a) With probability 0.95, what values of X are in the centered, symmetric range? Answer: 90.2, 109.8 b) What are the values of X that define the inter-quartile range? Answer: Using Z = 0.675, the values of X are 96.625, 103.375 8. X is a Normal random variable with a: 5. a) What is the probability that a value of the variable will be within 5 units of its mean? Answer: 0.6826 b) What happens to this probability if the standard deviation decreases to 2? Answer: Probability increases to 0.9876