This is a temperature conversion equation where -4 and 41 are Fahrenheit temperature limits.
Take the left inequality first: 9C/5>=-4-32, 9C/5>=-36, C>=-5/9*36, C>=-20.
Now the right: 9C/5<=9, C<=5. So -20<=C<=5.
To show this graphically first draw the graph F=9C/5+32 or y=9x/5+32. Establish the intercepts: y=32 and x=-160/9 (-17.8) and draw a line between the points (-20,-4) and (5,41). The line should pass through the intercepts.