The graph below represents the relationship between the amount of engine oil and the amount of gasoline that can be mixed in the engine of a chainsaw.

y = -0.04x + 17.2

Step-by-step explanation:

The y-intercept is the point where the graph crosses the y-axis.  In an equation in slope-intercept form, y=mx+b, it is b, the number added after the x.

Looking at our graph, we can see that the graph intersects the y-axis a little over 17; this means our y-intercept, given our choices, is 17.2.

The slope is the rate of change; in the slope-intercept form it is m, the number x is multiplied by.

In our graph, we can see that it goes from a little over 17 to 16 on the y-axis as it goes from 0 to 30 on the x-axis; this makes the slope about 1/30, or 0.03.  The line is decreasing, so the slope must be negative.  The closest match in our options is -0.04.

This makes the equation y = -0.04x + 17.2.

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