r-9s=2 add 9s to both sides
r=2+9s making 3r-3s=-10 become:
3(2+9s)-3s=-10 perform indicated multiplication on left side
6+27s-3s=-10 combine like terms on left side
6+24s=-10 subtract 6 from both sides
24s=-16 divide both sides by 24
s=-16/24
s=-2/3, making r-9s=2 become:
r-9(-2/3)=2 perform indicated multiplication on left side
r+6=2 subtract 6 from both sides
r=-4
So s= -2/3 and r= -4
