You can use the supplementary angle theorem to identify the angle above the base of the triangle.
We know that the degrees of a straight line is 180.
Now since a line is intersecting it, this divides 180 degrees into 2 parts, 1 part we see is 130 degrees. If we subtract 130 from 180, we get 50, the degrees of the top of the triangle.
A triangles angles always add up to 180, so if we subtract 50 from 180 which is 130
then divide that number by 2 (65) and you get your final answer.
