She earns $5.50 for every hour so:

3 hours and 45 minutes is 3.75 hours.


After rounding, she earns $20.63.
For this case we have an equation of the form:
f (w) = A * (b) ^ w
Where,
A: initial amount
b: growth rate
w: number of weeks
Substituting values we have:
f (w) = 400 * (1.05) ^ w
Answer:
the beetle population can be determined after a number of weeks, w, with the following function:
f (w) = 400 * (1.05) ^ w
Answer:
9/8
Decimal form: 1.25
Mixed Number form: 1 1/8
Good luck, hope this helped!