Who is faster The Flash or Quicksilver?

I want a source to back up your answer

The flash.

Step-by-step explanation:

He used to max out at Mach 1. Since crossover events are exceedingly rare, it is safe to assume that if you were comparing their speeds, the Flash is consistently faster than Quicksilver, though operationally speaking both could be consider comparable since their feats tend to be done at the same overall speed.