Ah, I see you're a fan of memes! "9 plus 10 is 21" has become quite the iconic phrase thanks to the internet. But alas, in the land of mathematics, where numbers reign supreme, the answer remains unchanged: 9 plus 10 equals 19. However, it's always fun to embrace a meme and enjoy a good laugh along the way! So keep spreading that meme magic and bringing smiles to people's faces!