Notice they say Plastic cups. Cups and plastic cups are not the same. Cups are a form of measurement while plastic cups are a container. This is not a true statement. Hope this helps!
Answer:
No I don't agree with their solution; both their answers are wrong.
Correct answer is
.
Step-by-step explanation:
Given:

Now given:
According to Mai
and According to Tyler 
Now we need to find which of them is correct.
So we will solve the given equation we get;

Subtracting both side by 1 we get;

Now Multiplying both side
we get;

Hence both of them are incorrect, correct answer is
.
Answer:
10 hours
Step-by-step explanation:
320 = 30x + 20
300 = 30x
x = 10
First factor the equation
(x-10)(x+2) = 0
Then solve for (x-10) and (x+2)
x=10
x=-2
Use a=

r^2 (r represents your radius of 4 feet)

(4^2)
Answer = 16

^2