How would you express an unknown number decreased by 12?

• A. x - 10
• B. 12 - x
• C. x - 12
• D. 12 + x

Answer: (C)

To express an unknown number decreased by 12 mathematically, you start with the unknown number, represented by a variable such as ( x ). The phrase "decreased by 12" indicates that you are subtracting 12 from this unknown number. Therefore, you would formulate it as ( x - 12 ).

This correctly captures the intended meaning since you take the unknown value ( x ) and subtract 12 from it, aligning perfectly with the phrase used in the question. This mathematical representation ensures that the expression reflects the operation described: starting from the unknown number and taking away 12 units. The other options do not accurately represent this operation, as they involve different numbers or a different structure that does not fit the phrase provided.