To solve the equation \(31 - 9x = 4\), we can follow these steps:
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Subtract 31 from both sides: \[ -9x = 4 - 31 \] \[ -9x = -27 \]
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Divide both sides by -9: \[ x = \frac{-27}{-9} = 3 \]
The solution of the equation is \(x = 3\).
Now, to express this solution in set notation, we denote the solution set containing the element \(3\). The correct set notation for the solution set is:
\[ { 3 } \]
The options given are:
- \({ 3}\)
- \({ x=3}\)
- \((3)\)
- \((x=3)\)
Out of these options, the correct one is \({ 3 }\) since it represents the set containing the solution \(3\).
Therefore, the correct answer is:
\({ 3 }\)