Final answer:
The function to calculate the number of illiterate people in Sylvania t years from today is P(t) = 9000 * (3/5)^t.
Step-by-step explanation:
To write a function that gives the number of illiterate people in Sylvania, P(t), t years from today, we can use the following formula:
P(t) = 9000 * (3/5)^t
This formula represents the reduction in the number of illiterate people by 3/5 each year. To calculate the number of illiterate people t years from today, we multiply the initial number of illiterate people (9000) by the reduction factor (3/5) raised to the power of t.