Hello, freakyfrog!
Are you skimming through some book?
This is a Linear Programming problem.
If this is an assignment, you should have been taught the procedure.
A tray of corn muffins takes 4 c milk and 3 c wheat flour.
A tray of bran muffins takes 2 c of milk and 3 c of flour.
A baker has 16 c milk and 15 c wheat flower.
He makes $3 profit per tray of corn muffins and $2 profit of bran muffins.
How many trays of each type of muffin should the baker make to maximize his profit?
Let = number of trays of corn muffins,
Let = number of trays of bran muffins,
Place the information in a chart:
. .
We have: .
[1] Graph the line:
. . Intercepts: (4,0), (0,8)
. . Shade the region below the line.
[2] Graph the line:
. . Intercepts: (5,0), (0,5)
. . Shade the region below the line.
The shaded region looks like this: Code:

8 *
*
 *
5 o *
:* *
:::**
:::::o
::::::**
::::::::* *
::::::::* *
  o     o  *  
4 5
We are concerned with only the vertices of the shaded region.
We see three of them: (0,0), (4,0), (0,5)
The fourth is the intersection of the two lines.
Solve the system and we get: (3,2)
Test these vertices in the profit function: .
. . and see which one produces maximum profit.
. .
For maximum profit, he should make 3 trays of corn muffins and 2 trays of bran muffins.