Like any good brain-teaser, the latest one bedeviling the internet looks pretty straightforward at first.
Using symbols of a horse, horseshoe and cowboy boot that equal specific numbers, the problem asks you to add them up and provide the sum after providing their values by answering three equations.
The brain-teaser has generated more than 500,000 answers on Facebook as people take their best shots, with many guessing 48. Others have guessed numbers as low as 12, but those are wrong, too.
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The first three equations show that a horse is worth 10, a horseshoe is worth 4, and a cowboy boot is equal to 2. That makes the fourth and unanswered equation 1 + 10 x 2, leading many to guess 22 as the answer.
But a trip back to your grade-school math book will lead to the correct answer, which is 21.
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According to the BODMAS (Brackets, Orders, Division, Multiplication, Addition, Subtraction) rule that determines the order of operations in math equations, you have to multiply or divide before you add or subtract.
So, instead of going from left to right, you have to multiple 10 x 2 first, and then add the 1, making the correct answer 21.
Now you can wake up in a cold sweat tonight after dreaming you didn't pass fourth-grade math and have a test tomorrow.
Follow TODAY.com writer Scott Stump on Twitter.