Question 135092
Sum of the angles in a triangle is 180.
Base angles of isosceles triangles are equal. They equal m
The vertex angle = {{{3m + 20)}}}
So

{{{180 = m + m + (3m+20) }}}
{{{180 = 5m + 20}}}
{{{160 = 5m }}}
{{{32 = m}}}
116 = vertex angle