I just don't get this problem, I feel I'm missing something obvious.
Poor attempt of solution:
I try to obtain an expression for x as a function of u and v, but I can't seem to be able to get anything from that system of equations.
From 1) I get , but from 2)
If I replace into 1)
I don't think I'm getting something from that
Another thought from there:
and I think I'm running in circles here.