A simple Kjarposko and its solution

Kjarposkos are a logic puzzle, also partly mathematical, invented in the Murderous Maths books. Named after series author Kjartan Poskitt, they consist of a set of boxes, each divided into upper and lower halves, connected with lines. The upper number in each box is equal to the total of the numbers in the lower half of every connected box, and the numbers to be put in the lower halves are shown alongside the puzzle.

The Kakuro and other Fiendish Number Puzzles book contains a total of 21 Kjarposkos of increasing difficulty until the last three, which have some of the upper-half numbers missing to make the puzzle even more difficult. Brand new Kjarposko puzzles of varying difficulty appear every day on the Murderous Maths site