Final answer:
To find the fraction of a day Sylvia spent driving to her cousin's house and back, add the fractions of a day she spent driving each way. Sylvia spent 5/6 of a day driving both ways.
Step-by-step explanation:
To find the fraction of a day that Sylvia spent driving to her cousin's house and back, we need to add the fractions of a day she spent driving each way. On Monday, she spent 5/12 of a day driving to her cousin's house. On Friday, she spent the same amount of time driving back home. So, the total fraction of a day she spent driving both ways is:
5/12 + 5/12 = 10/12 = 5/6
Therefore, Sylvia spent 5/6 of a day driving to her cousin's house and back.