Question

The masses of four planets in a solar system outside the Milky Way are given below.

Answer 1

Your answer is Planet B, Planet D, Planet A, Planet C. 
Look at the exponents.
23 comes before 24 and 27. So 3.30 x 10 ^ 23 comes first. Next, 24, and there are 2, so  go by the decimals, 4.87 comes before 5.97. So 4.87 x 10^24 comes before 5.97 x 10^24. Then, that leaves 1.89 x 10^27.