Both frogs and ducks have webbed feet. However ducks are more closely related to perching birds than to frogs.

Explain the process that has resulted in both frogs and ducks having feet that are similar

This would occur through the process of convergent evolution. This describes the independent evolution of similar traits in unrelated species. Some examples would be the development of a streamlined shape for swimming among fish, penguins, dolphins and seals. The development of wings for flying among birds and bats. And the development of complex eyes among vertebrates and cephalopods.