Treat the inequality like a normal equation; first, subtract #3# from both sides, then divide by #2#. Here's what the process looks like:
#3+2n>21#
#2n+3>21#
#2n+3color(blue)-color(blue)3>21color(blue)-color(blue)3#
#2ncolor(red)cancelcolor(black)(color(black)+3color(blue)-color(blue)3)>21color(blue)-color(blue)3#
#2n>21color(blue)-color(blue)3#
#2n>18#
#color(blue)(color(black)(2n)/2)>color(blue)(color(black)18/2)#
#color(blue)(color(black)(color(red)cancelcolor(black)2n)/color(red)cancelcolor(blue)2)>color(blue)(color(black)18/2)#
#n>color(blue)(color(black)18/2)#
#n>9#
That's the solution. Hope this helped!
