Implicit function question: Given that $u=f\big(x,y,g(x,y)\big)$, express $∂^2u/∂y^2$ and $∂^2u/∂x∂y$ using partial derivatives of $f$ and $g$.

Question

this is my first time using StackExchange so I don't really know if anybody would help me out but here I go! The question I had while solving practice questions for the [Implicit Function Theorem] is as follows. (The question's actually kinda short - same as the title)

"Given that $u=f(x,y,g(x,y))$, express $∂^2u/∂y^2$ and $∂^2u/∂x∂y$ using partial derivatives of f and g."

If anybody could help me out, I'd really appreciate it! Thanks x