Answer: s = -9
Solution:
18-7s=-9s to -7s=-9s-18 (change the sign of the constant [18] and then move it to the right)
Now move the variable (-9s) to the left side and change its sign as well (now it's just +9s)
Now we have -7s + 9s= -18
Combine the like terms (-7s+9s)
Now we have 2s= -18
And then divide both sides of the equation by two (which equals s = -9)
And then you have your answer, s = -9
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