Final answer:
The student has asked about the value of a variable in a system of equations. However, the given intersection point (-3, 1) does not satisfy the line's equation y = 3x + 9, suggesting an inconsistency in the provided details.
Step-by-step explanation:
The student is asking for the value of a variable within the context of a system of equations and graphs of lines. With the given information that the graphs of the lines intersect at (-3, 1), we need to identify the equation of the line that these coordinates satisfy. According to Figure A1, the slope-intercept form of the line's equation is given by y = mx + b, where m is the slope and b is the y-intercept.
The detailed example mentions that the y-intercept is 9 and the slope of the line is 3. This translates to an equation of the line y = 3x + 9. To find the value of x at the point where the lines intersect, we would substitute the given coordinates into this equation:
y = 3(-3) + 9
1 = -9 + 9
1 = 0
This shows us that there might be an inconsistency in the information provided since substituting the intersection coordinates (-3, 1) into the equation does not yield a true statement. It suggests that either the given intersection point or the y-intercept/slope information might be incorrect.