Either you use a table or technology to solve this problem. If you use technology, you need to use the right method given that technology and the answer is provided.

1) z = (x-mu)/sigma you are given x = 800 and mean (mu) and standard deviation (sigma)

2) You need to solve for x given that you look for the z value in a table that gives you .85 probability that the x is to the left (If you have a right tail table, you need to use .15). Once you have the z, you can use the definition of z in (1) to solve for x = sigma*z + mu.

3) same as (1), different x

4) Same as (2), but you want left of .14 or right of .86

5) Same as (1), then use the z to find the percentile (left tail).

The second part is just x = mu

Please consider a tutor.