Let the number of hours be x.
70 + 80x < 100x
20x > 70
x > 3.5
Answer:

Step-by-step explanation:
The formula of a volume of a cylinder:

r - radius
H - height
We have the radius r = 12cm and the height H = 20cm. Substitute:

The formula of a volume of a cone:

r - radius
H - height
We have the radius r = 8cm and the volume V = 2880πcm³. Substitute:

The answer is
y= - x-9/3 I believe.
1- Subtract 9 from both sides.
-3y = x - 9
2- Divide both sides by -3
y = - x-9/3