Typical consumer cameras starts the zoom at 35mm.
Dun be confused with "35mm camera" or "35mm equivalent focal length". The former means that the camera uses a film of size 35mm.(those widely used films.) The latter is more technical. Won't go into that yet.
So for a normal 35mm camera, with starting focal length at 35mm(widely available type), a 3x zoom camera will have focal length from 35mm to 105mm (note: 105/35 = 3).
Also note that:
For a normal 35mm camera, with starting focal length at 28mm(may be a bit more expensive), a 3x zoom camera will have focal length from 28mm to 84mm (note: 84/28 = 3).
Thus the more professional way of telling pple how much zoom your camera/lens have is to quote the focal length millimetres. Pls note that the larger the number, the "further" you can see.
For your qn: 18-55mm
In the case of the Canon 300D, the sensor size is not as large as the normal film(35mm film) everyone uses. it's slightly smaller. Thus if you look at it from another way, the image is actually cropped. That's where the "cropping factor" comes in. The 300D has a cropping factor of 1.6. The cropping factor differs from camera to camera. depending on the sensor/film size.
Thus when pple say "35mm equivalent focal length", he has already taken the cropping factor into account. So the 35mm equivalent focal length of the EF-S 18-55mm is from 28.8mm to 88mm.( 18x1.6=28.8, 55x1.6=88)