The expressions for \( x \) and \( y \) in terms of \( u \) and \( v \) are:
\[
x = -\frac{u}{5} + \frac{2v}{5}, \quad y = -\frac{3u}{5} + \frac{v}{5}
\]
The Jacobian determinant is:
\[
\frac{\partial(x, y)}{\partial(u, v)} = \frac{1}{5}
\]
Thus, the final boxed answers are:
\[
\boxed{x = -\frac{u}{5} + \frac{2v}{5}} \quad \text{and} \quad \boxed{y = -\frac{3u}{5} + \frac{v}{5}} \quad \text{and} \quad \boxed{\text{det} = \frac{1}{5}}
\]