Final answer:
To answer a mathematics question regarding linear equations, equiations A (y = -3x), B (y = 0.2 + 0.74x), and C (y = -9.4 - 2x) from the given choices are all linear equations.
Step-by-step explanation:
The question posed relates to systems of inequalities and their graphing, which is a topic commonly found within the study of linear equations in algebra. To determine which system of inequalities best describes a certain region where sillimanite can form, we would need to have information about the pressure-temperature conditions that define sillimanite stability fields. However, the provided question does not include such geological context, and instead provides a list of inequalities unrelated to the formation of sillimanite. Thus, to address this as a pure math problem, let's focus instead on identifying which of the given inequalities are linear, as per the reference information to 'Practice Test 4' about linear equations.
From the provided choices, the following equations are linear:
- A. y = -3x is a linear equation in slope-intercept form, with a slope of -3 and y-intercept at the origin.
- B. y = 0.2 +0.74x is also linear, with a slope of 0.74 and y-intercept at 0.2.
- C. y = -9.4 - 2x is linear as well, with a slope of -2 and a y-intercept at -9.4.
Therefore, the equations which are linear are A, B, and C.