15. Tom spends \( \frac{2}{12} \) hour bathing a day. Megan spends \( \frac{3}{12} \) hour a day bathing. How much more time does Megan spend bathing in 7 days than Tom?

In one day, Tom spends \( \frac{2}{12} \) hour bathing, which simplifies to \( \frac{1}{6} \) hour. Over 7 days, Tom bathes for \( 7 \times \frac{1}{6} = \frac{7}{6} \) hours. On the other hand, Megan spends \( \frac{3}{12} \), or \( \frac{1}{4} \) hour daily. In 7 days, Megan spends \( 7 \times \frac{1}{4} = \frac{7}{4} \) hours. To find how much more time Megan spends bathing than Tom over 7 days, we calculate: \[ \frac{7}{4} - \frac{7}{6}. \] To subtract these fractions, we need a common denominator, which is 12. Converting the fractions gives: \[ \frac{7}{4} = \frac{21}{12}, \quad \frac{7}{6} = \frac{14}{12}. \] Now, we can subtract: \[ \frac{21}{12} - \frac{14}{12} = \frac{7}{12}. \] So, Megan spends \( \frac{7}{12} \) hour more bathing than Tom over 7 days.