SOLUTION
(6) We want to find c in the diagram below
The triangle is a isosceles triangle since two sides are equal. So their base angles are equal. I have labelled their base angles as x
one of the x's makes a straight angle with 140. Angles on a straight-line is 180 degree so
[tex]\begin{gathered} x+140\degree=180\degree \\ x=180-140 \\ x=40\degree \end{gathered}[/tex]
sum of angles in a triangle makes 180 degree, so
[tex]\begin{gathered} x+x+c=180\degree \\ 40+40+c=180 \\ 80+c=180 \\ c=180-80 \\ c=100\degree \end{gathered}[/tex]
Hence the answer is 100 degrees
