Some <em>possible answers</em> are:
Three 8-hour shifts; four 6-hour shifts; six 4-hour shifts.
Explanation:
We want factors of 24 for the shifts, since the shifts cannot overlap. The factors of 24 include:
1, 2, 3, 4, 6, 8, 12, 24
A 1-hour shift does not make much sense; most employers will also not use a 2-hour or 3-hour shift. Restaurants typically do not use 12-hour shifts either, and employers do not use 24-hour shifts either. This leaves 4, 6, and 8.
If we use 4-hour shifts, we would have 24/4 = 6 of these shifts.
If we use 6-hour shifts, we would have 24/6 = 4 of these shifts.
If we use 8-hour shifts, we would have 24/8 = 3 of these shifts.