Question 7607
r-s=-3
r+s=9

add the two, and you'll get:
2r=6
{{{2r/2}}}={{{6/2}}}
r=3


In order to figure out the value of s, we need to multiply one set by -1
r-s=-3   -->{{{-r+s=3}}}
r+s=9    -->r+s=9


add the two and you'll get:
2s=12
{{{2s/2}}}={{{12/2}}}
s=6



r=3, s=6