Math puzzles challenge even the smartest people

Use your intelligence and calculation skills to find the answer behind the question mark. This question requires the answerer to be not only intelligent but also very careful.

So stay calm to avoid making mistakes like most players.

Can you give the correct answer to this question?

Quickly register yourself in the group of smartest people by leaving your answer in the comment box.

Trung Temple

Source: https://vtc.vn/cau-do-toan-hoc-thu-thach-ca-nhung-nguoi-thong-minh-ar836133.html