By definition, skew lines are a pair of lines that are not parallel but do not intersect each other either. Hence, the conclusion would be, the lines are non-coplanar. An example would two random lines drawn in the x and y axes in a cartesian plane, respectively.
You might want to stick to at most five questions at once, makes it easier for the rest of us. :)
17. T has a vertical line of symmetry (along the center line).
18. Z looks the same if you turn it halfway around.
19. The passes total to 150°, which is a little less than 180°, so I estimate it would be in front of Kai.
20. Left is the -x direction. Up is the +y direction. this is (x-6, y+4)
21. Every dilation has a center (where it's dilated from) and a scale factor (how much it's dilated).
22. It must be A, because it's the only one where the number of moves adds up to 16.
23. It can be determined to be B just by tracking where point C would end up through the transformation.
24. A 180° rotation flips the signs on both components to give you (-1, 6).
25. Right is the +x direction. Down is the -y direction. (x+3, y-5)
26. This is a reflection.
Need clarification on anything?
This is the definition of a rational number.
It's called a rectangle. This is just a definition, so there is not much to explain.
You can use a tangent:
We have opposite = 17 and adjacent = x.
substitute:
cross multiply
multiply both sides by √3
divide both sides by 3
Use the Pythagorean theorem:
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Other method.
triangle.
The sides are in the ratio 
Therefore
