Q1: Is a backpack used as a school bag a lot in the USA?
Q2: I don't know how to save money.
1. I can help you with that.
2. I can help you with saving money.
3. I can help you save money.
(Does #1 mean #2 or #3?)
Q1. Yes, indeed. =)
Q2.
#1 and #3 are the best answers for this question. #2 is not wrong; it's just wordy and not used much.