Can someone explain how to do #5 and 6?

Un used xx milliliters, or 90\%90%, of his favorite bottle of hot sauce. which of the following expressions could represent the volume of a full bottle of jun's favorite hot sauce, in milliliters? choose 2 answers: choose 2 answers: (choice a) a \dfrac{x}{0.9} 0.9 x (choice b) b \dfrac{10}{9}x 9 10 x (choice c) c 0.9x0.9x (choice d) d xx (choice e) e x+0.1x+0.1