Su doku. The number 1-9 Should be placed into the grids in such a way that each horizontal row and vertical column contains a different digit. In addition, each of the nine blocks of nine smaller squares should contain a different digit. There's no maths involved, no degree in science required, no adding up and no knowledge needed. You just solve each puzzle with reasoning and logic. As the puzzles get harder you will need to think ahead a bit more, but the key with these is practice.
Futoshiki puzzles can be solved by fitting the numbers 1 to 5 (or more in some of the harder puzzles) into each row and column, obeying the greater-than and less-than signs between adjacent squares.