Answer: 12 days
Explanation:
For us to know the number of days whereby Julie will have both basketball and track practice, we've to find the lowest common multiple of both 6 and 4. This will be:
Multiples of 4 = 4, 8, 12, 16, 24.
Multiples of 6 = 6, 12, 18, 24, 30.
The lowest common multiple is 12. Therefore, she'll have basketball and track practice in 12 days