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