In 2023, Sarah celebrated her 30th birthday, which means she was born 30 years earlier. To find her birth year, we can calculate: Sarah's birth year = 2023 - 30 Sarah's birth year = 1993 As for her younger sister, she is 5 years younger: Younger sister's birth year = Sarah's birth year - 5 Younger sister's birth year = 1993 - 5 Younger sister's birth year = 1988 So, the birth years are: Sarah: 1993 Younger sister: 1988