<PRE><B>Question 179764</B>
lets call our angles a,b and c . we will call angle a=20. since this is a bisector then b=c. we know that a+b+c=180
:
a=20.........eq 1
b=c..........eq 2
a+b+c=180....eq 3
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take value of a which is 20 from eq 1 and the fact that b=c and plug that into eq 3
:
20+b+b=180
:
2b=160
:
{{{highlight(b=80)}}}degrees
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solver is correct it would be 
:
it is the angle formed by the bisectors they are after here.
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That would be 180-(80/2)-(80/2)=100 degrees</PRE>