Question 87272
The systems of inequalities: (x represents # AM radios & y represents # AM/FM radios)
use four different colored pencils for shading so determining the feasible will be easy
1) 
15x+20y<300
-15x    -15x
20y<300-15x
everything over 20
y<15-3/4x or y<-3/4x+15
graph this start (15,0) then go down 3 and to the right 3 each time.
connect the points.
shade the area below the line
2)x>4
place the point (4,0) and draw a vertical line through the point.
shade the right area of the vertical 
3)y>3
place the point (0,3) and draw a horizontal line through the point.
shade on top of the horizontal.
4)
4x+3y<18
-4x   -4x
3y<18-4x
everything over 3
y<6-4/3x or y<-4/3x+6
place the point (6,0) then go down 4 then to the right each time
connect the dots then shade the area below the line.
FINALLY:
the part of the graph where all the shaded regions overlap is the feasible region.
HOPE YOU UNDERSTAND