Question 81512
Here is how to do the word problem part:

First convert the english language in the problem to math language.

I will do this in two steps

The first step is to line up the facts individually like this

Time to produce one AM radio = 15
Time to produce one AM/FM radio = 20
Total production time <= 300
Total radios produced <= 18
Number of AM Radios produced >= 4
Number of AM/FM Radios produced >= 3

The next step is to figure out the variables and constants.
We want to rewrite all the constraints in algebraic terms.
The problem states x is the number of AM radios and y is the number of AM/FM radios.
The last two facts are:
x >= 4
y >= 3

Facts 1 and 2 can be used to translate facts 3 and 4 into math.

"Total radios produced" is x + y

Total production time is:
  total time making AM radios
  +
  total time making AM/FM radios

Total time making AM radios is the number of AM radios multiplied by the amount of time needed to make an AM radio.  (Note: In a real factory, employees may not behave in a linear fashion.  However an assumption of linearity can be reasonable for a simple model.)

Total time making AM/FM radios is the number of AM/FM radios multiplied by the amount of time needed to make one AM/FM radio.

In math:
 Total production time: {{{T = 15*x + 20*y}}}
 Total radios:          {{{R = x + y}}}

Now all the constraints are:

  1. x >= 4
  2. y >= 3
  3. x + y <= 18
  4. 15 x + 20 y <= 300

Also it is true that x and y are whole numbers.

Also we know x, y, T, and R are all >= 0 so you might want to
graph that too.

I guess you already know how to graph - use the graphing tools on this site if it is a problem.  Or ask that part of the question again if that was the part you wanted help with.