What is the measure of a base angle of an isosceles triangle if its vertex angle measures 30?
30 150 15 75 18cm, 6cm, 13cm

It is 75!  Remember the vertex angle is the angle at the tip of the triangle. The two angles on the right and left are the base angles. In order to solve this you have to do 180-30 and then divide the answer by two! Remember all angles must add up to 180°

Hmm i believe it would be c