Two random variables $X$ and $Y$ have variances and covariance that satisfy the following relationships:
$Var(X) = 2Var(Y)$.
$Cov(X,Y) = Var(Y).$
Let $A = X+2Y$ and $B=2X+Y$.
Calculate the correlation coefficient between $A$ and $B$.
I'm not sure how to go about solving this question, any help would be appreciated. Thank you.