'All Indians are hardworking. All Punjabis are Indians. Therefore, all Punjabis are hardworking.' This argument is

The argument is valid; its conclusion follows necessarily from the premises.

All Indians are hardworking and all Punjabis are Indians.

Punjabis fall within Indians, and Indians within the hardworking.

So Punjabis must fall within the hardworking as well.

This is the valid first-figure form known as Barbara (AAA).