The Solution.
The given transformation is defined by the reflection below:
[tex](x,y)\rightarrow(-y,-x)[/tex][tex](-y,-x)+(+1,-2)=(-y+1,-x-2)[/tex]Reflecting 1 unit to the right and 2 units down, we have
[tex](-y,-x)+(+1,-2)=(-y+1,-x-2)[/tex]So, the required coordinates of the vertices are
[tex]A(3,6)\rightarrow A^{\prime}(-6+1,-3-2)=A^{\prime}(-5,-5)[/tex][tex]B(-2,6)\rightarrow B^{\prime}(-6+1,2-2)=B^{\prime}(-5,0)[/tex][tex]C(3,-3)\rightarrow C^{\prime}(3+1,-3-2)=C^{\prime}(4,-5)[/tex]