It is a mixed number because mixed mumbers have higher numerator than the denominator
Answer:

Step-by-step explanation:
√(-100)
Use the imaginary number rule 
√(-1) × √(100)
i × √(10²)
i × 10
= 10i
Assume Charles charges $7*3=$21 if he babysits for 2,5 hours (that is 2 and a half hours).
That is we are not considering Charles babysitting exactly 1, 2, 3 or 4 hours, but also in between times.
then we can write the following piecewise function to describe the situation:
f is a function from (0, 4] to {$7, $14, $21, $28}
Answer:
h≈2.12
Radius =9
volume = 180
Step-by-step explanation:

h=3V / πr2=3· 180 / π·9^2 ≈ 2.12207