What are the missing angles in this geometry problem?

[Ellieman]

Find the missing angles in each of the following:

 

[eumyang]

Need to show an attempt of these problems. What is the difficulty here?

 

[Ellieman]

Triangle: 180-129= 51
180-138= 42
A+51+42= 180
A= 180-51-42= 87 degrees

Regular Octagon: (8-2)180/8= 135 degrees

 

[Ellieman]

I am not sure how to find the angles for the other problems

 

[eumyang]

Are you familiar with this theorem?

If two parallel lines are cut by a transversal, the alternate interior angles are congruent.

You can use this for the top right and bottom right problem in your attachment.

Are you also familiar with supplementary angles?

 

[Ellieman]

180-38-100= 42

a is corresponding to y
z is the alternate exterior angle to a
x is supplementary to a
105+x= 180
x= 75
z= 105

180-30-70= 80
< 3= 80
I am not sure how to solve for < E and < A

 

[Ellieman]

120-180= 60

 

[eumyang]

180-38-100= 42

a is corresponding to y
z is the alternate exterior angle to a
x is supplementary to a
105+x= 180
x= 75
z= 105

180-30-70= 80
< 3= 80
I am not sure how to solve for < E and < A

You were also given three pairs of parallel lines. Use that, and the theorem I quoted in post #5, to find angles E and A.