I like my mum more than my dad.
Does this imply that 'I prefer my mum to my dad' Yes.
Does 'Australia is closer to Asia than America'
mean 'Australia is closer to Asia than it is to America' Yes.
Also, is saying
'I am more popular in Australia than in Japan'
a perfectly acceptable substitute for 'I am more popular in Australia than I am in Japan'? Yes.
Any help would be appreciated
Student or Learner