Lets turn each number into standard form.
4.35 * 10^20 = 435,000,000,000,000,000,000
4.84 * 10^19 = 48,400,000,000,000,000,000
4.9 * 10^19 = 49,000,000,000,000,000,000
4.84 * 10^19 < 4.9 * 10^19 < 4.35 * 10^20
Therefore, the numbers from least to greatest is 4.84 * 10^19, 4.9 * 10^19, and 4.35 * 10^20
Best of Luck!