It is the first one I believe

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No solution in real numbers.
Given :
The percent of concentration of a certain drug in the bloodstream x hours after the drug is administered is given by
.
To Find :
Find the time at which the concentration is a maximum. b. Find the maximum concentration.
Solution :
For maximum value of x, K'(x) = 0.

Since, time cannot be negative, so ignoring x = -3 .
Putting value of x = 3, we get, K(3) = 15/( 9 + 9) = 5/6
Therefore, maximum value drug in bloodstream is 5/6 at time x = 3 units.
Hence, this is the required solution.
Answer:
7 chocolate bars will cost $35
Step-by-step explanation:
if 3 cost $15 then 1 bar would cost 5 dollars and 5x7=35
here is a ratio:
<u>3</u> = <u>7</u>
15 = 35
first get all variables on the same side, then use elimination to solve.
x = -3
y = -11