Answer:
23
Step-by-step explanation:
Basically I did it backwards & opposites:
-28 divided by -7 = 4
4 + 19 = 23
I checked btw and it worked.
At any time
(min), the volume of solution in the tank is

If
is the amount of salt in the tank at any time
, then the solution has a concentration of
.
The net rate of change of the amount of salt in the solution,
, is the difference between the amount flowing in and the amount getting pumped out:

Dropping the units and simplifying, we get the linear ODE


Multiplying both sides by
allows us to identify the left side as a derivative of a product:



Integrate and divide both sides by
to get

The tanks starts off with 30 lb of salt, so
and we can solve for
to get a particular solution of

Answer:

Step-by-step explanation:
You are making rusks and have to dry them overnight at a temperature of 176° F.
The given temperature is in Fahrenheit. We need to convert it into °C.
The relation between Fahrenheit and °C is given by :

Put F = 176
So,

So, the temperature is equal to
.