A seemingly simple sum left the internet stumped as people scrambled to remember elementary arithmetic. 

The sneakily complex equation was posted on X last week by the account Break the Silos which regularly shares brain teasers. 

Brain teasers like this one are crucial to keep your memory sharp and problem-solving skills at play. 

See if you can recall elementary path principles to solve the following problem, which stumped dozens of amateur mathematicians: 5x8-9+7. 

The special rule to solve a compound equation like this one is taught in elementary classrooms across the country.  

Here's a hit: there's a specific acronym that spells out the exact order in which to solve each symbol.

Can you remember the decades-old rule and solve the problem as fast as possible? 

Ready, set, go!

How did you do? 

If you managed to recall the classic order of operations, solving this sum should have been a breeze. 

A handy acronym you may have learned in elementary school could have given you a hint on how to get the correct answer. 

PEMDAS stands for Parentheses, Exponent, Multiplication, Division, Addition and Subtraction. 

Since the problem does not contain parentheses or exponents, the first step to solve this sum would be multiplication. 

Since 5x8=40, the equation now reads 40-9+7. 

With no division to be seen, next in line are addition and subtraction. However, in PEMDAS one does not take precedence over the other. 

So it can then be solved from left to right, beginning with 40-9=31. 

And then the final part: 31+7=38. 

Did you get the answer right?  

If you were stumped, fear not, you were in good company. 

Some people may have made the mistake of solving addition before subtraction, because of the order in which they appear in PEMDAS. 

In that case, you may have started the sum on the right foot with 5x8=40. 

But then, things would have unraveled as you skipped to 9+7=16. 

That would have left you with 40-16=24, which is incorrect.