The guidelines of KenKen are as follows:

• You should fill within the numbers 1 by 6, one quantity per field, within the grid, so every row and every column incorporates every quantity precisely as soon as.
• Each closely outlined part of the grid is marked for you with a quantity and an emblem of an arithmetic operation. It signifies that the numbers to be positioned within the containers in that part, when mixed through that operation, yield the given quantity. For instance, if it says “60×”, then the numbers within the containers in that part should multiply to sixty. For division (“/”) and subtraction (“−”) there shall be exactly two containers within the part: considered one of them divided by the opposite should yield the the given quantity.

The following puzzle is taken immediately from Simon Tatham’s assortment (the place he calls the puzzle sort “Keen”). It’s one which I discovered unusually difficult, which is why I’m sharing it with you.