Answer:
Vertex angle = 124°
Explanation:
m<BAC = m<BCA (base angles of isosceles ∆ are congruent)
7x + 1 = 5x + 9
Collect like terms
7x - 5x = -1 + 9
2x = 8
divide both sides by 2
x = 4
Vertex angle = 180 - ((7x + 1) + (5x + 9)) (sum of triangle)
Plug in the value of x
Vertex angle = 180 - ((7*4 + 1) + (5*4 + 9))
Vertex angle = 180 - (29 + 29)
Vertex angle = 124°