If 3x = 12, then x = 4.
Multiplication Property of Equality
Two angles that have a sum of 180⁰
Supplementary angles
Premise 1: All men are mortal.
Premise 2: Socrates is a man.
Conclusion: Socrates is mortal.
True, valid, and sound
Type of reasoning that draws a conclusion after observing patterns in several examples
Inductive reasoning
If a number is even, then it is divisible by 2.
15 is not divisible by 2.
Therefore, 15 is not even.
Modus tollens
If 27⁰ = x, then x = 27⁰
Symmetric Property of Equality
Two angles that have a sum of 90⁰
Complementary angles
Premise 1: All birds are reptiles.
Premise 2: A sparrow is a bird.
Conclusion: A sparrow is a reptile.
Valid (the conclusion follows logically), but unsound (Premise 1 is false).
Given p → q, the ___ of the statement is q → p.
Converse
You get your license.
Modus ponens
If AB = CD, CD = EF
Then AB = EF
Substitution or Transitive Property of Equality
Nonadjacent angles of two intersecting lines
Vertical angles
Premise 1: The sky is blue.
Premise 2: Water boils at 100°C.
Conclusion: Therefore, the grass is green.
Argument is invalid. Premises do not support the conclusion. Unsound.
Given p → q, the ___ of the statement is not p → not q.
Inverse
If line l ∥ line m and line m ∥ line n,
then line l ∥ line n.
Transitivity
If angle A is congruent to angle B and angle A = 50⁰, then angle B = 50⁰.
Definition of congruent angles.
Two angles that share a common ray and endpoint but no common interior points
Adjacent angles
Premise 1: The Constitution states that anyone who has ever owned a cat is legally disqualified from running for President of the United States.
Premise 2: Candidate Jones has owned three cats in his lifetime.
Conclusion: Therefore, Candidate Jones is legally disqualified from running for President of the United States.
Valid but premise 1 is untrue; therefore, the argument is unsound
Given p → q, the ___ of the statement is
not q → not p.
Contrapositive
If the plant gets enough sunlight, then it will grow tall.
The plant did not grow tall.
Therefore, it did not get enough sunlight.
Modus tollens

Angle Addition Postulate
Two angles that have the same measure
Congruent angles
Premise 1: Senator Smith served honorably as a pilot in the United States Air Force.
Premise 2: The federal highway budget increased by four percent last fiscal year.
Conclusion: Senator Smith's proposed corporate tax reform bill will lower the national deficit.
True premises, Invalid, Unsound
The biconditional p ↔ q is true when
(p → q) Λ ______.
q → p
If a triangle is equilateral, then all three of its angles measure 60°.
Triangle ABC is equilateral.
Therefore, all three angles of triangle ABC measure 60°.
Modus ponens