You need to compare like with like, so the best common form is decimal, because it's easy to compare numbers. The set of numbers becomes: 0.23, -0.8, 0.20, 0.777...78. Negatives are less than positives, so -4/5 comes first, then 1/5, 0.23 and 0.777...78 (7/9). -4/5 has the largest magnitude but it's the smallest number because it's negative.