D.the number of times the drug has removed a certain percentage of fluid from the patient's lungs
Answer:
(√138)/24
Step-by-step explanation:

If we assume that point C is somewhere on segment AD, then,
AD = AC + CD
AD = (9x-12) + (4x+18)
AD = (9x+4x) + (-12+18)
AD = 13x+6 is the answer
Question 8 should be y=-5/2x-1. And question 9 should be y=1/2x-7.
First solve for one variable
(I chose bottom equation because it’s easier)
Get y alone: Y = 5x
Now that we have y we can plug y into the top equation
Plug in 5x for y: 2x + 5x = 7
Solve for x: 7x = 7
X = 1
Now plug in the x value into the bottom equation to solve for y
Y = 5(1)
Y= 5
So, x = 1 and y = 5