Determine the minimum required sample size if you want to be 95% confident that the sample mean is within 21 units of the population mean given o = 97.9. Assume the population is normally distributed.
What is the critical value that corresponds to a level of confidence of 95%?
Round your answer to two decimals.
What is the minimum sample size required for this problem?
Round your answer up to the next integer.

Value is 6 i think k

So the first thing we do is to multiply the top equation by 3. the reason i want to do this is i notice there will be a 6y on both equations and can possibly add/subtract them. so we get 6y = -3x + 27. adding that and the second equation we get 6x = 27-15 which is 12. divide by 6 and we get 2. ∴ x = 2. substituting 2 into the first equation we get 2y = -2 + 9 which is 7. divide by 2 and we get 7/2. ∴ y = 7/2, x = 2.