Standard form for a linear equation is usually written as \( Ax + By = C \), where \( A \), \( B \), and \( C \) are integers, and \( A \) should be non-negative.
Let's analyze each option:
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\( x - y = -7 \): This can be written as \( 1x - 1y = -7 \). Here, \( A=1 \), \( B=-1 \), and \( C=-7 \). The equation is in standard form, though \( C \) is negative, which is allowed but not typical for standard form.
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\( 0.1x + 0.25y = 7 \): To convert this to standard form, we can multiply through by 100 to eliminate the decimals: \( 10x + 25y = 700 \). Now, \( A=10 \), \( B=25 \), and \( C=700 \). This is in standard form.
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\( x + y = 7.5 \): This can be expressed as \( 1x + 1y = 7.5\). However, \( C \) is not an integer, which does not satisfy the standard form requirements.
Based on this analysis, the equations \( x - y = -7 \) and \( 0.1x + 0.25y = 7 \) can be considered as being in standard form; however, the most appropriate candidate that strictly adheres to the standard form convention (with integer coefficients) is:
\( 0.1x + 0.25y = 7 \) (after multiplying through by 100).
Thus, among the options, the one that fits standard form best after modification is:
0.1x + 0.25y = 7 is in standard form after multiplying by 100, resulting in \( 10x + 25y = 700 \).
So the best answer here is:
0.1x + 0.25y = 7.