1. The problem states that the shape is reflected in the y-axis. 2. Reflection in the y-axis changes the x-coordinate of any point from $x$ to $-x$, while the y-coordinate remains the same. 3. The vertex A is originally at the coordinates $(2,3)$. 4. Applying the reflection rule, the new coordinates of vertex A after reflection are $(-2,3)$. 5. Therefore, the vertex A maps to the point $(-2,3)$ after reflection in the y-axis.