I will explain, what you need to know, to solve this.
For the first sheet:
a.) You have a given E[X] = 0.5 and want to find the value of a, use the definition of E[X], which is a sum that is equal to 0.5, e.g. E[X] = -2*p(-2) + ... + 4*p(4) = 0.5
b.) Also similar to a.) use the definition of Var[X] = E[X^2] - E[X]^2
c.) Plug in the terms in the definitions an solve the equations
d.) Rewrite 4X^2 > Y to X > sqrt(Y)*2 --> sqrt(Y)*2 < X, how does one calculate P(X < x) for discrete random variables?