The standard form of a linear equation is typically written as \( Ax + By = C \), where \( A \), \( B \), and \( C \) are integers, and \( A \) should be non-negative.
Let's examine each of the provided equations:
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−x + 2y = 12
This can be rewritten as \( 1x - 2y = -12 \), which is not in proper standard form, as A should be positive. -
x + y = −12
This can be rewritten as \( x + y = -12 \). Here, A (which is 1) is positive, but \( C \) is negative. This isn't the typical standard form we reference. -
x + 0.5y = 12
This is not in standard form because of the coefficient \( 0.5 \); A should be an integer.
Since none of the provided equations strictly conform to the standard form format with A, B, and C as integers, the correct answer among the options is:
None of these are in standard form.