Question 147908
First you have to get the equation into y=mx+b form. {{{3x+4y<=12}}}.  First change it to {{{3x+4y=12}}}.  Then solve for y and get {{{y=-(3/4)x+3}}}.  Graph that line:
*[invoke describe_linear_equation 3, 4, 12]

Now since it was originally {{{3x+4y<=12}}}, shade every part of the graph under that line.  Then you're done.

If you still need help, visit my lesson on graphing inequalities:
http://www.algebra.com/algebra/homework/Graphs/Inequalities-Made-Easy.lesson