Can someone please explain this math?

Question

I asked a question here
http://answers.yahoo.com/question/index?qid=20070307065652AAaIm5f&r=w

While I was told I was right I need to know how to get the answers. Me and a friend worked on it and I dont have the paper we did it on. And now I am lost as how we came to the answers.

Answer 1

sorry to reply so late i was offline. well u will be needing these formulae.
mean= (sum. X)/n
var = (sum ( X-mean)^2)/n
S.d= sqt(var)