I ususally go to the gas station once a week, but using economically, the gas lasts 2weeks.

여기서 but 부분이 분사구문이잖아요. 원래형태로 쓴다면 어떻게 써야하나요?
주어는 I 인가요? 답엔 used 인데... 주어가 I 면안될거같아서요... ㅜㅜ 또하나더

having heard that the tickets for the concert were sold out, i was dissapointed.

에서요분사구문은 바꿔쓰면 had heard 인데 that 절은 그냥 과거 로 놔두면 되나요?? 막 헷갈려요 ㅜㅜ