The fractions can be ordered by finding a common denominator and comparing the numerators. In this case, the common denominator is 18. After converting the fractions, we get 6/18, 9/18, 10/18, and 12/18. Comparing the numerators, we can see that 6/18 is the smallest, followed by 9/18, 10/18, and 12/18. Therefore, the fractions can be ordered as 1/3, 1/2, 5/9, and 4/6 from least to greatest.