For this case, we have a function of the form:
![y = P (m)](https://img.qammunity.org/2020/formulas/mathematics/middle-school/jrusfg7mqlsewbhz7986g90881q8yynl09.png)
Where "y" represents the number of problems completed.
We must find the inverse function of:
![P (m) = \frac {m} {4} +7](https://img.qammunity.org/2020/formulas/mathematics/middle-school/pnwaodphpjejjt0pylkqzl161rmnihy28i.png)
For this, we perform the following steps:
We change P(m) to y:
![y = \frac {m} {4} +7](https://img.qammunity.org/2020/formulas/mathematics/middle-school/dttc10k9d3cnugbvn7ptyfv514bhmylpp3.png)
We clear the variable "m":
![y-7 = \frac {m} {4}](https://img.qammunity.org/2020/formulas/mathematics/middle-school/2k3pv11n1wkqw05f58uwzljk0648ftc9v4.png)
![4 (y-7) = m](https://img.qammunity.org/2020/formulas/mathematics/middle-school/mnxbnp6n30o9ziy3xns6w6xj8hisdqn4xt.png)
We change m to
:
![4 (y-7) = f ^ {- 1} (m)\\f ^ {- 1} (m) = 4y-28](https://img.qammunity.org/2020/formulas/mathematics/middle-school/smznx8vtakm8im31admop5ztcf6i8j7enx.png)
Taking into account that "y" represents the number of problems completed, we substitute "y" for "p":
![f ^ {- 1} (m) = 4p-28\\M (p) = 4p-28](https://img.qammunity.org/2020/formulas/mathematics/middle-school/iuwag41nzlfn9jbnjh45ddphunicl47j9h.png)
Answer:
Option D