Go Bulbasaur, Psyduck, and Sandslash!

Psyduck versus Cubone! Psyduck has a type advantage, Psyduck wins!

Bulbasaur versus Geodude! Ground is super-effective against Bulbasaur's poison. HOWEVER, Bulbasaur's Grass is x4 effective against Geodude's Rock and Ground types!
So, pretty much, it's a draw.

Finally! Sandslash versus Onix! Both are final evolutions! BUT! Sandslash's Ground typing is super effective against Rock types! Sandslash wins!

SO! I win!