where are the statements so i can help
Answer:

For this case we know that
represent the radius,
the height and the rate given is:


And replacing we got:

And that represent 
Step-by-step explanation:
For a tank similar to a cylinder the volume is given by:

For this case we know that
represent the radius,
the height and the rate given is:

For this case we want to find the rate of change of the water level when h =6m so then we can derivate the formula for the volume and we got:

And solving for
we got:

We need to convert the rate given into m^3/min and we got:

And replacing we got:

And that represent 
6z-7z/5=3
(30z-7z)/5=3
30z-7z=15
23z=15
z=15/23
1. N + 2; n = 6: the answer is 8 because n=6 so we sub n with that... and we get 6+2 and that’s 8.
2.5f; where f=4: the answer is 20 because when a variable is directly next to a number it is multiplied by that number so we will replace f with 4 and our equation is now 5(4) or 5•4 and both are equivalent to 20.
3. 7b-2; where b=5: the answer is 33 because 7 multiplied by 5(b) minus 2= 7(5)-2 or 7•5-2= 33 because you will multiply 7 by 5 and get 33 then you will subtract by 2 and get 33.
Hope this helps!!!
The middle is 2 :D hope this helps