3d Geometry

Let the mirror image of the point (a, b, c) with respect to the plane 3x \(-\) 4y + 12z + 19 = 0 be (a \(-\) 6, \(\beta\), \(\gamma\)). If a + b + c = 5, then 7\(\beta\) \(-\) 9\(\gamma\) is equal to ______________.