Classic brain training methods are perhaps puzzles like crosswords or sudoku, but in recent times, I have become more and more attracted to the type of challenge you’ll see below.

These types of puzzles have been flooding the web lately, probably because they are fun!

These are old classic mathematical problems. When you were in middle or high school.

These tests are more fun when you find yourself trying to remember the math you learned as a child.

Can you solve this equation – without a calculator?

Okay, now to the challenge.

Below is a tricky equation. Can you solve it without using a calculator?