Just some definitions:
$X,Y$ are random variables
$\mu_X = E[X]$
$\text{cov}(X,Y) = E[(X-\mu_X)(Y-\mu_Y)]$
Given $\text{cov}(X,X)$ and $\text{cov}(X,Y)$, what can be said about $\text{cov}(Y,Y)$?
For example, if $X$ has low variance, and $\text{cov}(X,Y)$ is high, then I would expect $Y$ to have low variance too.