Answer:
1. If NI is nickel, then AU is gold.
Converse: If AU is gold, then Ni is nickel.
Inverse: If Ni is not nickel, then AU is not gold.
Contrapositive: If Au is not gold, then Ni is not nickel.
2. If two angles form a linear pair, then they are supplementary.
Converse: If two angles are supplementary, then they form a linear pair.
Inverse: If two angles did not form a linear pair, then they are not supplementary.
Contrapositive: If two angles are not supplementary, then they did not form a linear pair.
3. If the points lie on the same line, then they are collinear.
Converse: If the points are collinear, then they lie on the same line.
Inverse: If the points did not lie on the same line, then they are not collinear.
Contrapositive: If the points are not collinear, then they did not lie on the same line.
