"친구를 가르쳐주는 것은 어려워요."
Translation:Teaching a friend is hard.
Not much, but 힘들다 is more physically difficult (strenuous, laborious) where 어럽다 is more mentally difficult (complicated, challenging).
Also, sometimes you use 힘들다 to mean it is hard, but you can achieve it with greater effort, where 어럽다 would imply you failed because of your lack of ability.
Is there a grammatical rule that explains why it's 가르쳐주는 instead of 가르치주는?
It's because of conjugation. 주다 (to give) attaches directly to the Casual form of the verb, so 가르치다 becomes 가르쳐 (ㅣ + 어요 = ㅕ요, drop the -요 to form Casual form) + 주다 + 는 것.
Ah! So essentially it's 가르치어주는 which then gets shortened to 가르쳐주는? I get it now. Thanks!
Considering 어려워요 is often translated as "difficult," that should be accepted here too.
Why is "것은" required in this sentence. Can it be omitted and make sense in Korean?