What is another, more informal way to say I am answerable to [somebody] as in the sentence:
I am answerable only to President.
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
Answerable to someone means being accountable to someone (or responsible to someone for something), in the sense that you must answer for your actions, if someone asks.
I don't know that there's a more informal direct alternative (e.g. single word substitution). The sentence you cited (I'd add "the")
I am answerable only to the President.
is basically saying that the subject ("I") doesn't have to explain his/her actions to anyone but the President. In fact, that might be one possible answer:
I don't have to explain my actions to anyone but the President.
Except that sounds kind of snotty and immature. The word answerable somehow seems to avoid that.
I'm not sure that answerable is really that formal, however. It's just one of those idioms used in the context of organizational responsibility.