Problem 9
List any three points that are on the same straight line.
So for example, you could say A, P and B. Or you could say C, P, and D. A third one you could do is J, D and K.
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Problem 10
Now we're listing any three points that aren't on the same straight line.
One example of such triple is A, P and D. Another example is K, D, and C. There are many others as well.
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Problem 11
List any four points that are in the same plane. So you'll pick four points from the set {A, B, C, D, P} to answer this question as these five points are all in the shaded plane R.
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Problem 12
Pick any four points such that they do not all exist in the same plane. It doesn't matter which points you pick as long as J or K are one of the points selected. This is because neither J nor K are in the plane R.
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Problem 13
Line JK intersects CD at point D. The other line that crosses CD is line AB.
Line AB is in plane R, while line JK intersects the plane at point D only.
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Problem 14
Intersecting line JK and plane R results in point D. This is where the line and plane meet, as mentioned in the previous problem.
If you were asked to intersect line AB and plane R, then you would get line AB as a result. All of line AB is inside the plane.
is a closed surface. We have
is the space enclosed by the surface 
