theorom 4 triangle =180

Question 1

given

Answer 1

triangle woth angle marked 123
trough a is line (DE)
DE parralel BC

Question 2

given

Answer 2

triangle woth angle marked 123
trough a is line (DE)
DE parralel BC

Question 3

required to prove

Question 4

proof

Question 5

required to prove

Question 6

proof