Detailed instructions for working a group puzzle of type 'TicTac-789'

The 3 elements in each group of this type of puzzle are: 7, 8, and 9.

Every group in the puzzle must contain exactly this set of elements.

Each row is a group numbered as shown in this TicTac-789 figure.

In a TicTac-789 puzzle, each row is a group numbered as shown in the figure above.

Each column is a group numbered as shown in this TicTac-789 figure.

In a TicTac-789 puzzle, each column is a group numbered as shown in the figure above.