Answer:
D. -1/3
Explanation:
Solve for y. Your answer is the resulting x-coefficient.
4.5y = -1.5x +18
y = (-1.5/4.5)x +18/4.5
y = -1/3x +4
The slope is -1/3.
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You can see that the graph of it has a "rise" of -1 for each "run" of +3. Then rise/run = -1/3 = slope.