Trigon puzzle
Trigon Puzzles are logic puzzles created by Alan Fraser-Dackers for Trigon Puzzles Ltd and are published on their own website and by Dell Magazines.
Trigon Puzzles are logic number puzzles that are widely variable. They come in many different shapes and the degree of difficulty varies.
The diagrams consist of a set of triangular dominoes made up from the available number sets. The number in the center of each domino shows the total of the numbers on the edges. Where dominoes meet the numbers in the neighboring sides are the same. When this number is filled in the space in the side of the triangle it must be suitable for both dominoes. By using logic, you fill in the numbers around each triangular domino.
There is always only one correct answer to the puzzle. The puzzles always have an adjoining table showing all the possible combinations of numbers, which can be crossed off so that the solver can keep track of which combinations are still available for use.
Strategy
The 0 can only be one combination, 000. This is typically the first domino to be filled in and crossed off. Depending on the size of the puzzle, you can do the same with the highest combination of numbers, whether it is 333, 444, 555, or 666. This will sometimes lead to solving (or partly solving) neighboring dominoes. For instance, if one side of the 18 (666) domino connects to a 7 domino then the solver knows that one side is a 6, therefore it must be the 016 domino. It takes more information to determine the orientation.
In general, finding neighboring dominoes with large differences in value will help solve the puzzle. As more dominoes are determined, the limiting of choices will make further solving easier, as well.