The base angle of an isosceles triangle measures 54°. what is the measure of its vertex angle?

27°
36°
54°
72°

Because this is an isoscele triangle wo this mean that the angles from the base are congruent what mean that than one angle has measure of 54 degree - given - so the second angle from the base has a measure of 54 degree too 

we know that the sum of angles of a triangle is equal 180 degrees so the vertex angle has a measure of 180 -(54+54) = 180 -108 = 72 degrees

Need the graph to answer this.

Yea they are simplyfiy the ratios