the some of an Isosceles triangle is 180.
if vertex B = 130 degrees then the other two must be equal 50 degrees. so you divided 50 by 2 which equals 25.
in this case you have 2 points which equal 50. so you take the one which is the closest to 25. which is the last point. m<A = 20 and m<C + 30.
I hope this is right.
