396 ? 556 99 872 664
I tried to solve it but to no avail. Possible answers are 666, 491, 654, 999 and 917; since, the exam was multiple choice we were offered potential answers. The helpless hints I used while trying to solve it are: 872 -> 664, there 8x8=64; 99 -> 872, there 9-1=8 and 8x9=72; but I couldn't go further. Thanks beforehand. If you read until here then I want to provide correct answer, since the company themselves showed correct answers today(13th June 2020) but I don't know why that is correct: 917.
Source: The question appeared on MetYös 2 exam yesterday (12th June 2020 7pm Istanbul time). It is a classical university entrance preparatory exam in Turkey for foreigners. I don't want to give link to their website here, and I don't want to increase their organic search ranking. I even don't want to mention their company name and exam, but rules here force me to do that which may indirectly contributes to that company's advertising. So, dear moderators, how can I cite the source without making pr of them? Thanks.