9s plus 3=57 pls help me

Your ultimate goal is to get the variable secluded all by itself.  You'll have to use the opposite operation to do this and remember, what you do to one side, you have to do to the other.
1. 9s + 3 = 57
2. Subtract 3 from each side. This will result in 9s = 54
3.  To undo the multiplication of 9s you'll divide both sides by 9.  9s/9 = 54/9
4.  The ending result is: s=6
5.  Go back and check your work by substituting it in your original equation.