Hello from MrBillDoesMath!
Answer:
96 degrees
Discussion:
The base angles of an isosceles triangle are equal and a triangle has 180 degrees. In our case this means that
42 + 42 + (measure of vertex angle) = 180
84 + (measure of vertex angle) = 180 => (subtract 84 from both sides)
84 - 84 + (measure of vertex angle) = 180- 84 =>
(measure of vertex angle) = 180- 84 = 96
Thank you,
MrB
