Answer:
x = 5
Explanation:
Since the base angles are congruent then the triangle is isosceles with the 2 legs being congruent, then
9x - 5 = 4x + 20 ( subtract 4x from both sides )
5x - 5 = 20 ( add 5 to both sides )
5x = 25 ( divide both sides by 5 )
x = 5