17.2.Lifetime (in hours) of a device is described by a r. variable with Normal distribution with parameters µ = 200 hours, variance σ2 = 400. What is the mean lifetime?
Further compute, with the help Excel (or of table of N(0,1) distribution function)

1. probability that device survives 180 hours;

2. such time that 90% of devices survive it (i. e. compute the 10% quantile of the distribution);
Write the density function of this normal distribution.

Well, what do you understand about this problem? Do you understand how to change from the given information to the "standard normal distribution"? Do you know how to use "Excel" (I don't!) or a table of the standard normal distribution (a good one is at Maths is Fun - Can't Find It (404)

Well the problem is that I dont really know how to solve this problem at all. I have never studied math like this and need help with understanding the process.

Why have you been given problems about the normal distribution if you have never studied the normal distribution?