Math problem baffles the internet—can you solve it?

If you’re anything like me, you’re probably grateful that the last time you had to wrestle with a tricky math equation or decipher an algebraic puzzle was back in high school!

I know some people are naturally drawn to math, while others—myself included—would rather steer clear of it. I’ve always seen myself as more of a creative thinker than a numbers person. But hey, to each their own.

That said, while I never enjoyed crunching numbers in a crowded classroom full of rowdy classmates, I’ve surprisingly found a certain charm in tackling online brain teasers when I come across them. There’s no pressure, no deadlines—just the satisfaction of figuring things out at my own pace.

And I’m clearly not alone. Turns out, there’s an entire community of people who take pride in spotting patterns and solving tricky math problems.

With that in mind, we decided to put our readers’ problem-solving skills to the test with a brain-teaser that has left countless people across the internet utterly perplexed.

So, are you ready to challenge yourself? Got your thinking cap on? Because here comes this week’s dose of mathematical gymnastics:

If 1 + 4 = 5, 2 + 5 = 12, and 3 + 6 = 21, then what is the value of 5 + 8?

Here it is written out for clarity:

1 + 4 = 5
2 + 5 = 12
3 + 6 = 21
5 + 8 = ?

This puzzle has sparked debates across the internet, with many people unable to agree on the correct answer. The key? It all depends on how you approach the problem—because, surprisingly, there’s more than one valid solution!

If you’ve already given it a go and want to check your answer (or if, like me, curiosity has gotten the better of you), take a look below at one possible method of solving it.

Solution 1

Using this pattern:

• 1 + 4 = 5
• 2 + 5 = 2 + 2(5) = 12
• 3 + 6 = 3 + 3(6) = 21
• 5 + 8 = 5 + 5(8) = 45

Algorithm: A + A(B) = C
Answer: 45

But wait—there are multiple ways to solve this puzzle! Think you found a different approach? Let’s explore a few more solutions…

Solution 2

This approach follows a pattern where each equation builds on the previous result:

• 1 + 4 = 1 + 4 + (0) = 5
• 2 + 5 = 2 + 5 + (5) = 12
• 3 + 6 = 3 + 6 + (12) = 21
• 5 + 8 = 5 + 8 + (21) = 34

Algorithm: A + B + C’ = C, where C’ is the previous answer.
Answer: 34

This method follows a cumulative sequence, making it a completely valid alternative solution. But is there yet another way to solve it? Let’s find out…

Solution 3

This approach follows a pattern where each result builds upon a modified sequence:

• 1 + 4 = 5 = 5
• 2 + 5 = (5 + 2) + (5) = 12
• 3 + 6 = (7 + 2) + (12) = 21
• 5 + 8 = (9 + 2) + (21) = 32

Algorithm: for {X=5, C = X + C’, X = X+2}; where C’ is the previous answer. A and B are not used in the equation.
Answer: 32

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Solution 4

This method uses number bases to determine the result:

• 1 + 4 = 5 (Base 10, so remains 5)
• 2 + 5 = 7 (Converted to Base 5) = 12
• 3 + 6 = 9 (Converted to Base 4) = 21
• 5 + 8 = 13 (Converted to Base 3) = 111

Algorithm: for {X=6, C = (A + B)^(10 -> X), X -1} (First answer in Base 6, then Base 5, then Base 4, etc.).
Answer: 111

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Solution 5

This method also uses different number bases but accounts for an additional missing number in the sequence:

• 1 + 4 = 5 (Base 10, remains 5)
• 2 + 5 = 7 (Converted to Base 5) = 12
• 3 + 6 = 9 (Converted to Base 4) = 21
• 4 + 7 = 11 (Converted to Base 3) = 102
• 5 + 8 = 13 (Converted to Base 2) = 1101

Algorithm: for {X=6, C = (A + B)^(10 -> X), X -1}, including “missing” numbers.
Answer: 1101

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So, there you have it—five different ways to solve the puzzle, each with its own logic. The beauty of this brain teaser is that it challenges the way we approach problem-solving. Which method made the most sense to you? Or did you come up with a completely different answer?