Several members of The Legion Of Super-Heroes are visiting Clark Kent's high school, because why the hell not, and it's time for Brainiac-5 to show these 20th century rubes how primitive they are!
Brainy, I can understand--he'd love to show off that way.
But the teacher's brother? Why would you even go through a math textbook you had written and spend "weeks" trying to add up all the figures in the book? Was this before they had invented hobbies, or "a life"??
And does that total include page numbers??
And this is a high school mathematics book--surely there are plenty of problems with decimals and fractions and irrational numbers and even π...what is the likelihood that the sum ended in a nice, round whole number?
And did he include the book's ISBN number?
And...how the hell does the guys sister happen to remember exactly the 17-digit number her brother came up with once? I mean, really?
And...13.9 quadrillion? Honestly? Let's say that's a 600-page text book. That means the average total of all the numbers on each page is 23.1 trillion!!! What the hell were they teaching our youth in 1964? (In fairness, maybe there's one page with a problem whose answer is 13.89 quadrillion, which would really skew the average...)
Of course, since this isn't our universe's Brainiac-5, there's a fair chance that he's wrong, because--
Oh, wait, I didn't mention? This is an alternate universe, where the Legion (or at least these 5 members) are EVIL!!
From Superboy #117 (1964)