Diophantus of Abae was a very smart man who lived a long time ago in ancient Greece. He was very interested in mathematics, which is all about numbers and how they work together.
Now, Diophantus was really good at solving problems that involved equations. An equation is like a puzzle where you have to figure out what the missing number is. So if 3 + __ = 7, you would know that the missing number is 4.
But Diophantus didn't just solve easy equations like that. He worked on really tough ones where the missing numbers could be really big and complicated. They were so hard that even other really smart people at the time couldn't solve them.
So Diophantus wrote a big book called the “Arithmetic.” It had lots of problems with equations that he had solved, and he was very proud of it. In fact, he was so proud that he put a little puzzle at the beginning of the book.
The puzzle was about his life. It said that he had lived for a certain number of years, and then there were some clues about how old he was when he got married and how long he lived after that. From all of these clues, you could figure out how old Diophantus was when he died.
Now, the thing is, Diophantus didn't actually tell anyone how old he was when he died. He just left the puzzle there and let people try to figure it out for themselves. And even though it took hundreds of years, someone finally did figure it out.
So that's who Diophantus of Abae was. He was a really smart guy who loved mathematics and wrote a book full of really tough problems. And he even left a little puzzle for people to solve after he was gone.