Let ( X ) and ( Y ) be two discrete random variables. (a) Calculate ( P(Y-X leq 5) ) (b) Calculate ( Eleft(Y^{2} mid X=15 ight) ). (c) Calculate ( operatorname{Var}(2 X-3 Y) )

i have the answers but i don't know how to solve it

Let X and Y be two discrete random variables. X=5 15 30 Y = 10 0.1 0.25 0.15 Y = 20 0.3 0.2 0 (a) Calculate P(Y-X 5) (b) Calculate E(Y2|X = 15). (c) Calculate Var(2X-3Y)