Now that i think about it, i wonder same in life as well.

1967B1 - Reverse Card (Easy Version)

if a+b ⋮ b*gcd(a,b) then a ⋮ b*gcd(a,b) so gcd(a,b) is b therefor a⋮b^2

p.s i didn't get the editorial so someone telling me it would be nice as well