I have two linear maps $X: \mathcal{L}(G) \rightarrow \mathbb{F}_q^k$ and $Y: \mathcal{L}(2G) \rightarrow \mathbb{F}_{q^n}$, where $G$ is a divisor of the rational function field $F_q(x)$ over $\mathbb{F}_q$ and $\mathcal{L}(G)$ is the Riemann-Roch space of $G$. Currently, I am stuck on computing the inverse maps $X^{-1}$ and $Y^{-1}$. I know I need to use the bases of the two Riemann-Roch spaces and solve linear combinations but I am unsure on exactly how to do this. Any help would be much appreciated.
Edit:
$X$ is defined as follows: For a function $f \in \mathcal{L}(G)$, $f(P_i)$ is computed on $k$ rational places $P_1,..,P_k \in F_q(x)$.
$Y$ is defined as follows: For a function $f \in \mathcal{L}(2G)$, $f(P)$ is computed on a place $P \in F_q(x)$ of degree $n$.