Sumdoku Set 7 8: Tips, Tricks and Strategies.

Tips:

• Start by identifying the rows, columns, and regions with the most given numbers. These will provide a good starting point.
• Look for common patterns, such as pairs or triples of numbers that can only go in specific cells within a region.
• Pay attention to the sum clues in the regions. These can often help narrow down the possibilities for the remaining cells.
• Use the process of elimination. If you've determined that a certain number must go in a particular row, column, or region, eliminate it as a possibility from other cells in that group.

Tricks:

• Naked Pairs and Triples: If you find two or three cells in a row, column, or region that can only contain the same two or three numbers, you can eliminate those numbers as possibilities from other cells in that group.
• Hidden Pairs and Triples: Sometimes, a pair or triple of numbers might only appear as possibilities in a certain row, column, or region. You can then eliminate those numbers as possibilities from other cells in that group.
• X-Wing: Look for rows or columns where a number can only appear in two cells. If those cells form the corners of a rectangle, you can eliminate that number as a possibility from other cells that share the same rows or columns.

Strategies:

• Sum Clues: Utilize the sum clues to work out the possible combinations of numbers in the region. This can often lead to deductions that help you fill in more cells.
• Locked Candidates: If you have a number that can only go in a certain row or column within a region, you can eliminate that number as a possibility from other cells in the same row or column in other regions.
• Guessing and Backtracking: If you've exhausted all logical deductions, you might need to make an educated guess on a particular cell's value. If it leads to a contradiction, backtrack and try a different value.

Remember, practice and patience are key to mastering Sumdoku Set 7-8. Each puzzle is a unique challenge, so keep honing your skills!