Create a function that takes a number and return a list of three numbers: half of the number, quarter of the number and an eighth of the number.
half_quarter_eighth(6) ➞ [3, 1.5, 0.75]
half_quarter_eighth(22) ➞ [11, 5.5, 2.75]
half_quarter_eighth(25) ➞ [12.5, 6.25, 3.125]
The order of the list is: half, quarter, eighth.