KenKen is like sudoku. The numbers 1 - n fill the columns and rows of an n x n grid.
Numbers are further constrained, to obey certain mathematical operations.
Two numbers inside a box marked 3- would have to differ by 3. e.g., 5 and 8 in some order.
Three numbers in a box marked 15x would have a product of 15. 1, 3 and 5 in some order.
Here is an 8x8 KenKen puzzle where the boxes are just marked with a number, like 3 or 15.
The mathematical operation is not specified. You have to figure that out as part of the puzzle.
One hint is that a boxes that contains more than 2 numbers must be either add or multiply.
Boxes that are marked 1 must be subtract: the other operators would require identical numbers or zero.
Each box should be solved as completely as possible before solving rows or columns.
A box with 1 number contains the marked number.
A box with 2 numbers marked 15 could be either 3x5 or 7+8. Nothing else.
A box with 2 numbers marked 12 could be 2x6, 3x4, 4+8 or 5+7. Only the number 1 would be excluded.
A box with 3 numbers marked 12 permits all eight numbers.
And so forth.
This KenKen puzzle is one that I have not been able to solve.
A gold star to anyone who solves it.
Good luck