<PRE><B>Question 920979</B>
The measure of an exterior angle at vertex B of isosceles triangle ABC is 70°.
So the measure of the vertex angle is 90-70 = 20 degrees
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The base angles have equal measure, so::
2x + 20 = 180
2x = 160
x = 80 degrees (measure of each base angle.
Cheers,
Stan H.
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 The measure of a base angle of the triangle is 
(1) 110° (2) 70° (3) 55° (4) 35°</PRE>