How to turn -1.5 into a fraction

What is the percent of increase for a population that changed from 438,000 to 561,000

Read the excerpt from gilgamesh: a new english version.gilgamesh backed away. he said,"how dreadful humbaba's face has become! it is changing into a thousand nightmarefaces, more horrible than i can bear.i feel haunted. i am too afraid to go on." §enkidu answered, "why, dear friend,do you speak like a coward? what you just saidis unworthy of you. it grieves my heartwe must not hesitate or retreat."

What is the inverse of the function f(x)=19/x³ ?