I can't answer this because I don't know what she was starting with
K/9 > 1/3
i believe this is how it is represented.
You have a line:
y=mx+b (slope-intercepted form)
m=slope of this line.
The slope of a line perpendicular to that given line will be: ´"m´"
m´=-1/m.
For example:
y=8x+3
m=8
The solpe fo a line perpendicular to "y=8x+3" is:
m`=-1/8
R = {10; 15; 20}
S = {20; 25}
R U S = {10;15; 20; 25;