Let's take a walk down memory lane - straight to geometry class (sorry). A Twitter user posted a photo of a mind-boggling triangle brain teaser, and people are now questioning their basic math skills.

Exactly how many triangles can you count in this fun triangle puzzle?

Do you think you have sharp eyes and an even sharper brain? Here’s a fun challenge that will put your observation and problem-solving skills to the test! Optical illusions are not just fun to look at ...