You can put this solution on YOUR website! 4s-12=-5s+51
To begin you need to add 5s to both sides;
4s+5s-12=-5s+5s+51
9s-12=51
then you +12 to both sides;
9s-12+12=51+12
9s=63
Finally you divide 9 on both sides.
9s/9=63/9
Your answer is:
s=7
Hope you understand =)