For many readers, it may have been a long time since middle school math class. However, a seemingly simple “middle school” math equation is circulating online, and it’s baffling netizens for one particular reason: it is actually a little more complex than it looks.

Before revealing the solution, here’s the equation that is getting people talking: 1 + 1 + 1 – 1 x 2 – 0 = ?

Can you solve it without a calculator?

In the age of technology, the temptation may be to reach for a calculator, cell phone, tablet, or computer keyboard to help you solve this math problem, but this time, please refrain from doing so. Take a few moments to find the answer, and when you think you have it, scroll down below to see the solution.

On the face of it, the equation looks simple. Many people believe that the answer to 1 + 1 + 1 – 1 x 2 – 0 = 4, and they reach this conclusion by addressing each function of the equation in order, from left to right. But is this correct?

Unfortunately, it is not.

The correct answer to this math problem lies within a decades-old mathematical principle known as the “order of operations,” which is a set of rules that dictate which part of the equation needs to be tackled first, and that matters, because problems solved in different orders can sometimes produce very different results. So, in order for everyone to be on the same page, rules were created to determine the order that math problems are to be solved.

Math teachers in the United States help their students to remember the order of operations using an acronym: PEMDAS, which stands for Parentheses, Exponents, Multiplication and Division, and Addition and Subtraction. As per this rule, math problems are to be solved in that order; “multiplication and division” are considered as being in the same category, as are “addition and subtraction,” and problems in the same category, as per this rule, are to be solved from left to right.

So, if we apply PEMDAS to our equation, what is the answer to 1 + 1 + 1 – 1 x 2 – 0 = ?

As there are no parentheses nor exponents, so we begin with multiplication, 1 x 2, which equals 2, and so we are left with 1 + 1 + 1 – 2 – 0 = ?

Next, since addition and subtraction have equal priority, we tackle the remainder of the equation from left to right.

1 + 1 = 2

2 + 1 = 3

3 – 2 = 1

1 – 0 = 1. The correct answer is 1!

Finding the answer was pretty simple after all. However, it was crucial to start with the multiplication according to the order of operations. Do you remember this procedure from middle school math class?

For those who did, this challenge is an exercise in affirmation; for those who didn’t, consider sharing this tricky math problem with friends, family, and coworkers to see how many people you know who possess prowess in mental arithmetic.

According to mathematician Steven Strogatz, writing for The New York Times, the order of operations is universally respected. No professional mathematician, he speculates, would ever submit an “ambiguous equation” to their peers.

Mathematicians routinely insert parentheses into their equations in order to make sure everybody understands which functions should be tackled first. For netizens who deduced the correct answer without parentheses, therefore, bravo!

Even in the age of technology, we use mental arithmetic every single day. Subconsciously, many of us use mental arithmetic to calculate totals such as hours spent at work, calories eaten, or minutes of cooking time on the clock.

Technology is fallible, yet math puzzles, as well as being loved by millions, might just help ensure that nobody is thwarted by simple mental arithmetic.