.
Since the angles are corresponding, m < 1 = m < 2, which gives you an equation
45 = x + 25
with the solution x = 20 degrees.
Solved.
On corresponding angles, see the lesson
- Parallel lines
in this site.
Also, you have this free of charge online textbook on Geometry
GEOMETRY - YOUR ONLINE TEXTBOOK
in this site.
The referred lesson is the part of this online textbook under the topic
"Basics of angles. Supplementary, complementary angles. Vertical angles. Parallel lines".
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