Question 1137048
.
<pre>
180° - 100° = 80°.     <U>ANSWER</U>
</pre>

Supplementary angles are those that sum up to 180°.


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On supplementary angles, see my lessons

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Angles/Angles-basics.lesson>Angles basics</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/geometry/How-to-solve-problems-on-suppl-compl-or-vertical-angles-Examples.lesson>HOW TO solve problems on supplementary, complementary or vertical angles - Examples</A>

in this site.


Also, &nbsp;you have this free of charge online textbook on Geometry

&nbsp;&nbsp;&nbsp;&nbsp;<A HREF=https://www.algebra.com/algebra/homework/Triangles/GEOMETRY-your-online-textbook.lesson>GEOMETRY - YOUR ONLINE TEXTBOOK</A> 

in this site.


The referred lesson is the part of this online textbook under the topic 
"<U>Basics of angles. Supplementary, complementary angles. Vertical angles. Parallel lines</U>".


Save the link to this online textbook together with its description


Free of charge online textbook in GEOMETRY
https://www.algebra.com/algebra/homework/Triangles/GEOMETRY-your-online-textbook.lesson


to your archive and use it when it is needed.