Well, Raid, if you really want to get pedantic about it, focal length isthe physical distance which separates the rear nodal point of an infinity-focused lens from the image plane onto which the light passing through the lens is focused. Thus, focallength is an intrinsic property of a lens, and is unaffected by the mount format or the size of the sensor in the camera body to which the lens is attached. So, there is a 15mm gap in focal lengths between the 55mm long end of the 17-55mm and the 70mm wide end of the 70-200mm, because 70mm - 55mm = 15mm.


When you mount a 70-200mm lens on a crop body, photo elves do not magically transform it into a 112-320mm lens - the focal length remains 70-200mm, but you get the angles of view equivalent to a (hypothetical) 112-320mm lens on a FF camera. So, if you want to compare FF-equivalent angles of view, then Dr. Croubie is correct and there is a FF-equivalent gap of 24mm (i.e. the gap between 27-88mm and 112-320mm). It's irrelevant that the EF-S 17-55mm cannot mount on a FF camera, since when mounted on a crop body, it yields angles of view equivalent to a (hypothetical) 27-88mm lens on a FF camera.


Raid, it occurs to me that you might have a misconception about EF-S lenses (a fairly common one), that because they mount only to APS-C bodies, their focal lengths are 'corrected' for the APS-C sensor format, such that 55mm on an EF-S lens optically different from 55mm on an EF lens, so that the former gives the same angle of view on APS-C as the latter on FF. But, that's not the case - 55mm is 55mm, regardless of camera or mount format - it just results in a narrower angle of view on an APS-C camera.


So, my original statement, that the 17-55mm + 70-200mm provides coverage from 17-200mm with a 15mm gap, is technically correct. Since the OP has an APS-C camera, that statement could also be phrased as FF-equivalent coverge from 27-320mm with a 24mm gap.