3(3s+4) = 24
Apply the Distributive Property:
9s + 12 = 24
Subtract 12 from each side:
9s = 12
Divide both sides by 9:
s = 12/9 = 4/3 as an improper fraction or 1 1/3 as a proper fraction or 1.33 as a decimal.
You don't say how the answer should be written so I provided all 3.