A math puzzle circulating on social media is stumping users with a set of equations that look wrong at first glance, according to the Ukrainian outlet UNIAN. The puzzle, published on 15 September, shows 2 + 3 = 10, 3 + 4 = 14 and 4 + 5 = 18, and asks solvers to work out what number should replace the question mark in the final line, 5 + 7 = ?
Under standard arithmetic, none of the equations add up. Two plus three equals five, not ten, so the puzzle's creators built in an extra step that solvers need to spot before the numbers make sense.
How to solve it
Puzzles built this way rarely require a complicated formula. Comparing several rows at once usually reveals a single rule that applies equally to all of them, rather than a separate trick for each line.
Solvers are advised to start with the first example: two plus three makes five, then work out what operation turns that five into the ten shown in the puzzle. The same operation should then be tested against the second and third rows, to check whether it produces fourteen for three and four, and eighteen for four and five, before being applied to the final sum of five and seven.
According to UNIAN, puzzles of this kind are designed to test attentiveness, logical thinking and the ability to spot patterns, and they typically do not require anything beyond a few basic arithmetic steps. That combination of simplicity and a hidden catch is part of why such brainteasers spread quickly online.
The correct answer
The rule behind the puzzle is straightforward: add the two numbers together, then multiply the result by two.
Checked against each line, two plus three equals five, and five multiplied by two equals ten. Three plus four equals seven, and seven multiplied by two equals fourteen. Four plus five equals nine, and nine multiplied by two equals eighteen.
Applying the same rule to the final line, five plus seven equals twelve, and twelve multiplied by two equals twenty-four. The correct answer is 24.
