Substitution vs Transitive

[Chocolate]

< means angle and * means degree

Statement: If <A + <B = 180* and <B + <C = 180*, then <A = <C.
Reason: Substitution/Subtraction

Why wouldn't it be Transitive/Subtraction?

Substitution property: If a=b, then "a" may replace "b' OR "b" may replace "a"

Transitive Property: If a=b and b=c, then a=c

Subtraction property: If a=b, then a-c=b-c

 

[TchrQbic]

< means angle and * means degree

Statement: If <A + <B = 180* and <B + <C = 180*, then <A = <C.
Reason: Substitution/Subtraction

Why wouldn't it be Transitive/Subtraction?

Substitution property: If a=b, then "a" may replace "b' OR "b" may replace "a"

Transitive Property: If a=b and b=c, then a=c

Subtraction property: If a=b, then a-c=b-c

Possibly the authors of the text were thinking of "<A + <B = 180" as a = b. Also "<B + <C = 180" is c = b. Then they considered the result as replacing 180 with <B + <C , or substitution. Interpretation is in how you're viewing what was done.