To solve the equation \( 31 - 9x = 4 \):
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Subtract 31 from both sides: \[ -9x = 4 - 31 \] \[ -9x = -27 \]
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Divide by -9: \[ x = \frac{-27}{-9} = 3 \]
The solution to the equation is \( x = 3 \).
Now let's analyze the answer choices given in terms of set notation:
A. {3} - This correctly represents the solution as a set containing the number 3.
B. (3) - This is not a standard notation for expressing a solution set.
C. {x=3} - This is also not standard; it represents a set containing the statement \( x = 3 \), not the solution itself.
D. (x=3) - This is not a correct representation of a solution set.
The correct answer, expressing the solution set in proper set notation, is:
A. {3}