Question 878669
Let x = the measure of the base angle



There are two congruent base angles in the isosceles triangle. The 3 angles of the triangle must add to 180 degrees. This means, {{{x+x+50=180}}}, solve for x to get



{{{x+x+50=180}}}



{{{2x+50=180}}}



{{{2x=180-50}}}



{{{2x=130}}}



{{{x=130/2}}}



{{{x=65}}}



So the base angle is 65 degrees. This is an interior angle. We want an exterior angle. So if y is an exterior angle to the 65 degree angle, then



{{{y+65=180}}}



{{{y=180-65}}}



{{{y=115}}}



Making the final answer <font color="red">(C) 115 degrees</font>