The statement "9+10=21" is not accurate mathematically; it is a meme or internet joke that originated from a Vine video that went viral. In the original video, a child is asked what 9 plus 10 equals, and they humorously respond with "21" instead of the correct answer, which is 19.
The video gained popularity on the internet and became a meme, leading to people sharing it and using the phrase "9+10=21" humorously in various contexts, often to poke fun at the incorrect answer or to reference the Vine video itself.
It's essential to remember that, in mathematics, 9+10 indeed equals 19, and this meme is simply a lighthearted joke that has spread online for entertainment purposes.