I've never seen a problem like this before. We're given that $E[X^2]=20$ and that the mean and variance of $X$ are equal. The task is to find the mean and variance given this information.
I wish I could say I tried everything, but I'm honestly clueless as to where I should even begin. I tried setting $Y = X^2$ to rewrite the random variable, but I don't think that helps at all.