Hi there, I'm struggling to understand how to do this as my teacher thinks it fine to not teach us and just give us lecture notes instead. I can understand the normal distribution but not the exponiental, any help will be greatly aprecciated.

I don't understand the formula, what is the e?

The example my teacher gave me is 'a computer monitor lasts 10 years before developing a fault, the average number of failures is 1 every 10 years, so 0.1 probability of a failure a year.

Then using exponiental distibutution she comes out with a figure of 0.3935, which I don't really have a clue as to how to do it.

I'lld love any help, thanks.