Calculating angles II

This task is about angle properties with lines.
Calculate the angles in the following diagrams and give a reason for your answer.
Lines marked are parallel.

Question 1Change answer

a)  Calculate the size of the angle marked r and give a reason for your answer.
Calculating angles with lines diagram 1  [Not drawn to scale]
r =  º
Reason:

Question 1Change answer

b)  Calculate the size of the angles marked s and t and give a reason for each answer.

Calculating angles with lines diagram 2 [Not drawn to scale]
s =  º
Reason:
  
t =  º
Reason:

Question 1Change answer

c)

Calculating angles with lines diagram 3  [Not drawn to scale]
Are the lines marked m and n parallel? YesNo
Give a reason for your answer: