oh right, i forgot to mention that X, and Y are independent.

i'm not understanding how to multiply normal distributions by constants,

is 4*X~N(3,5) = X~N(12,20) ?

EDIT: i now get Z~N(43/3, 20.011) is this right?

and i think i figured out the covariance

Cov(X,Z)=Coz(X,4X-1/3*Y)

=Coz(X+0Y,4X-1/3*Y)

=4Cov(X,X)-1/3 Cov(X,Y)

=4Var(X)-1/3(0) <--- by independence

=4Var(X)

=4*5

=20

Is this right?