She has studied Geography for 3 years.
→She started  studying Geography 3 years ago.
2.I was very tired, so I couldn't cook dinner
→ Because I was very tired, I couldn’t cook dinner.
3. It is very noisy in the city but we enjoy living there.
=> Although  it is very noisy in the city, we enjoy living there.
4. Although I was late, I didn't miss the bus.
=> In spite of being late, I didn’t miss the bus.
5. I often walked to school when I was a student.
=> I used  to walk to school when I was a student.