Answer:
21%
Step-by-step explanation:
Formula for this type of problem is

cross multiply

divide by 400

/400 /400

plug 21 into the original equation

simplify

.21 can be represented as 21%
2c-9=c
-9=-c
9=c
Hope that helps!
Answer:
Step-by-step explanation:
5+n+4+7+n+8=360
24+2n=360
2n=360-24
2n=336
n=168
Solution: We are given an urn contains 1 red chip and 1 white chip.
Now let's consider the first draw.
The probability of drawing red chip 
We know that if the first chip drawn is red, we will put back that chip into the urn with additional two red chips. So if the first chip drawn is red, we will have 3 red chips and 1 white chip in the urn.
Now if we draw another chip from an urn containing 3 red chips and 1 white chip. Then the probability of drawing a red chip is

Now lets combine these two events
The probability of both are red = P(1st draw is red) . P(2nd draw is red)
=(1/2) x (3/4)
=(3/8)
Therefore, the probability of both selections are red is 3/8
I believe the answer is A. because the theory of continental drift and sea-floor spreading causes new rock to form and creates the old rock .. older