By coincidence, CYOA #39 was Supercomputer by Edward Packard, published in 1984, which was the last CYOA that I ever got. Guess I was aging out of them by then. Fond memories of the early series, though.
Depends on which infinities. For example, the amount of even numbers and the amount of even+odd numbers are both infinity (aleph null). so the set of all even numbers is the same size as the set of all even and odd numbers. However the set of all numbers between 0 and 1 is infinitely larger than either of those (aleph one).