Hey, Could you please explain #21(practice test #7)

Sure. This question is asking you for the predicted increase in the y-value on the graph for an increase on the x-value. In other words, it’s asking you for the slope!

So let’s pick a couple points that look close to the given line of best fit and calculate the slope. There are no places on the graph where the line of best fit perfectly hits the grid lines, but I think we can say that the line looks like it goes through (11, 20) and (24, 40). What’s the slope given those two points?

\text{slope}=\dfrac{y_2-y_1}{x_2-x_1}=\dfrac{40-20}{24-11}=\dfrac{20}{13}\approx 1.54

That doesn’t precisely equal any of the answer choices, but it doesn’t have to! Remember, the question says “which of the following is closest,” and 1.54 is very close to choice C: 1.5. So that’s what we go with.

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