Inky is a Japanese puzzle invented by Tetsuya Miyamoto. It is known with many different names, some of which are Mathdoku, Calcudoku and KenKen. In Inky you are given a square grid which you have to fill with numbers, so that no number appears twice in a row or a column. Additionally, if you sum/subtract/multiply/divide the numbers in an outlined region (depending on the given sign), the result should match the number shown in that region.
The Inkies below are shared by KrazyDad, a website with thousands of various types puzzle problems.
Remark: All materials are copyrighted, for personal use only. If you want to use any of them for a book, app, website or periodical, please contact the authors first.