An example of homologous organs is:

Homologous organs are those which have a common ancestor but have evolved differently and adapted suitable functions according to their needs. Our arm and dog’s foreleg has the basic structure of bones but they have different functions, a dog uses it for walking while human beings use it for holding/ grasping.

Our teeth and elephant’s tusks again have same structure but they serve different functions. Likewise, potatoes and runners of grass, both grow underground but they have different uses, potatoes serve as food whereas grass as vegetation.