Get ready for your brain to hurt. Again.
A math teacher in Vietnam challenged his third-grade class (read: 8-year-old students) to solve this seemingly simple arithmetic problem.
Apparently you're supposed to plug in the numbers 1 through 9, using each digit once, in each of the blank spaces. Using the identified operations and the inserted values, a correct answer would lead to a solution of 66 (those double dots stand for division, by the way).
Sound easy? Try it.
Teacher Tan Phuong gave the puzzle to his students in the town of Bao Loc, according to local outlet VN Express. He said he also sent the exercise to a person with "a doctorate in economics with mathematics" who has yet to return with a solution, The Guardian reported.
So, what's the answer?
The Guardian's Alex Bellos has promised to upload a solution "later," but if anyone has an easier approach, leave it in the comments.