They can only be chosen in six orders:
They are:
(1). smallest number, middle-size number, largest number.
(2). smallest number, largest number, middle-size number.
(3). middle-size number, smallest number, largest number.
(4). middle-size number, largest number, smallest number.
(5). largest number, smallest number, middle-size number.
(6). largest number, middle-size number, smallest number.
Only (1) is in increasing order, so the probability is
1 way out of 6 or 1/6.
Edwin