[An abundant number is a positive integer $n$ whose divisors add up to more than $2n$. For example, $12$ is abundant because $1 + 2 + 3 + 4 + 6 + 12 > 24$.]
There is a theorem that states that: " The product of two distinct primes is not abundant". Here is a proof. [Found here: https://www.lboro.ac.uk/media/media/schoolanddepartments/mathematics-education-centre/downloads/research/SE-booklet.pdf]
I am puzzled how one can proved this theorem by contradiction. Thanks in advance for any help.