It was the seemingly simple maths puzzle that left the Internet baffled.
The equation, which uses flowers instead of numbers, went viral with thousands of Facebook users debating the correct answer.
Daily Mail Australia put it to Associate Professor Leon Poladian, from the University of Sydney's mathematics department, who came back with a solution - but even he had to admit, it was a bit of ahead-scratcher.
Professor Poladian noted that the 'trick' to the puzzle lay in that the blue flower on the final line only had four petals, not five.
In the puzzle, which is posted as a graphic, there are three lines showing what different combinations of flowers add up to. Then a new combination is shown, with no total, and it's up to people to work out the answer.
Wrong: People have given a number of different answers on the Facebook posts, with many of them incorrect
Because the puzzle tells us that the red flower is worth 20, a blue flower with five petals is worth five, and two yellow flowers are worth two.
In the final line there is one yellow flower added to one red flower multiplied by one blue flower with four petals, making the equation 1 + 20 x 4.
最后一行中是一朵黄色小花加上一朵红色小花与一朵四瓣蓝色小花的乘积，因而由1 + 20 x 4可算得答案，即81。
However, Professor Poladian did warn that puzzles like this can have more than one correct answer, as there is not enough information to confirm that the number of petals on a flower changes its value.
If you were to disregard the number of petals on the blue flower, you would come up with an entirely different answer of 101.