Answer:
9
Step-by-step explanation:
Since the axis of symmetry is vertical and the vertex of the parabola is at (12,-4), the vertical line x=12 is the axis of symmertry. The x-distance between the axis of symmetry and the first x intercept (15,0) is equal to 15-12=3. Hence, this x-intercept is 3 units to the right of the axis, and because it is symmetric, the other x-intercept must be 3 units to the left of the axis, so its x-coordinate must be 12-3=9. Then, the other x-intercept is at the point (9,0)
