Help Me Please On The Normal Distribution!

[Senoritaaa]

I CAN'T DO IT TO SAVE MY LIFE!:
The random varialbe x has the discrete uniform distribution over the set of consecutive intergers {-7, -6... 10}
calculate
a)the expectation and variance of x
b) P (x>7)
c) the value for n for which P(-n<x<n)=7/18

 

[ssd]

This is not a Normal Distribution question. Prob on each mass point is 1/18.
a)Just sum (-7)+(-6)+....+9+10 and divide by 18 to get the expectation.
Find {2(1+4+9+16+25+36+49)+64+81+100}/18. Subtract square of the expectation from this ans to get variance.
b)3/18, since here only 3 values of x=8,9,10 satisfiy x>7.
c)3