Velocity of X-ray is:
X-rays are electromagnetic radiations with following properties:

Velocity = 3 x 108 m/sec or 2 lakh miles/sec
They cannot be focused, reflected or refracted.
They cast the shadow of the objects falling in their path.
They are affected by electric and magnetic field.

Ref: Karjodkar 3rd Ed, Pg-72
1 lakh miles/sec
2 lakh miles/sec
3 lakh miles/sec
0.5 lakh miles/sec