Final answer:
The population of gerbils in 8 days is 328.
Step-by-step explanation:
The population of gerbils in a pet store can be modeled using the function y = 400 - 9x, where x is the number of days.
To find the population of gerbils in 8 days, we need to substitute x = 8 into the equation and solve for y.
Substituting x = 8 into the equation, we have:
y = 400 - 9(8)
Simplifying, we get:
y = 400 - 72
= 328
Therefore, the population of gerbils in 8 days is 328.