The knitter who sold 9 hats sold 4 scarves
Here, we want to know the number of scarves a kinitter who sold 9 hats sell
What we do here is to go to the axis that represents the number of hats sold
From the diagram, this is the x-axis
Now, identify the point at which we have 9 hats. We no trace up and identify the marked point
From here, we can trace to the vertical axis
With proper tracing, we can see that 9 hats correspond to 4 scarves