Final answer:
In the young adult novel 'Illuminae,' Kady is introduced as being 17 years old.
Step-by-step explanation:
In the book Illuminae, the main character Kady Grant is introduced as being 17 years old at the start of the story. Kady's age is significant as it sets the stage for the young adult eponymous space saga where she, along with others, must navigate a complex universe of corporate intrigue, hacking, artificial intelligence, and an intergalactic war.
Her journey of survival and the challenges she faces as a teenager in such extreme circumstances capture the essence of the character's development throughout the series.