1) Number of vertices are same in both.
2) Number of edges are same in both.
3) Each vertex has degree=4 in both.
Now place 7 vertices using the same structure as in original graph and mark the numbering in clockwise order as: $\left \{ 1,6,4,2,7,5,3 \right \}$.
Using graph (b) (the numbered graph in above pic), place edges between the newly placed vertices.
NOTE: The edges are to be placed using graph (b).
You can clearly get the original graph.
Hence both are ISOMORPHIC.