Answer:
6 or 3mL/hr, probably 3mL/hr
Step-by-step explanation:
If dopamine makes up half of the solution then you half the total mL/hr to 3. If it is the whole solution then it tells you the answer (6mL/hr). I'm not sure if the question is poorly worded or just how you typed it but it would be easier to answer if it was clearer.
Given

To find the missing value in the diagram.
Now,
From the diagram the value of x is 5.
Then, substitute the value of x in the given equation.
That implies,

Hence, the missing value is 7.
B) Find the possible values of $z$ in exponential forms