Sarah was born in 1993. To determine this, let's reason through it step-by-step: 1. In 2023, Sarah celebrated her 30th birthday. This means she turned 30 that year. 2. Her younger sister, who is 5 years younger, couldn't attend because she was studying abroad. 3. If Sarah is 30 in 2023, then her younger sister would be 30-5=25 years old. 4. Since the sister is 5 years younger and also celebrating a birthday that year, that means the sister is turning 25 in 2023. 5. Therefore, Sarah was born in the year 2023 - 30 = 1993. So Sarah was born in the year 1993.<|end_header_id|>