I need help with these three problems (college algebra)

5. After 6 hours, the concentration is halved. After 12 hours, it will be quartered. If the original concentration is 200 nmol, a quarter is 50 nmol.

14. The population doubles after 3 hours, and a day is 24 hours. That means that the original population should be multiplied by , or . 3 million times is 3 * 256 million, or 768 million.

15. The concentration is halved every 8 hours and the original concentration is 100 nmol. So now, how many times do you halve 100 to get to 12.5?

100/2 = 50, 50/2 = 25, 25/2 = 12.5. That's three times. 3 * 8 is 24 hours, or 1 day.

5 50 nmols

14d 768 million

15 a 1 day

Step-by-step explanation:

5. We can use ratios to solve this

At 6 hours there is 100 nmols in the system

For each 6 hours, we decrease by 1/2

As 12 hours  there will be 1/2 of this amount in the in the system so 1/2(100) = 50 nmols

14. 0 hour = 3 million

We double every 3 hour

3 hour = 2*3million = 6 million

6 hours = 2*6 million = 12 million

9 hours = 2*12 million = 24 million

12 hours = 2*24 =48 million

15 hours = 2*48 = 96 million

18 hour = 2*96 = 192 million

21 hour  = 2 * 192 =384 million

24 hour = 1 day = 2 *384 = 768 million

15   0 hours = 200 mg = 100 nmols

We divide by 2 every 8 hour

      8 hour                        50 nmols

    16 hours                        25 nmols

     24 hours  =1 day           12.5 nmol

step-by-step explanation:

this is not a question

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18