This triangle is an isosceles triangle because it has two congruent sides. Therefore, the two bottom angles are also congruent. And, the sum of the interior angles of a triangle is 180 degrees.
180 = 104 + (9x - 25) + (9x - 25)
180 = 104 + 18x - 50
180 = 54 + 18x
126 = 18x
x = 7
Hope this helps!