The "X" multiplier zoom is simply the longest focal length divided by the shortest and is a misleading number with very little value, even when properly understood, unless you know ether the tightest or widest focal lengths. A 5 to 50mm focal length zoom is technically a 10x zoom, but doesn't cover all that big of a range. A 70 - 400mm zoom on the other hand is barely even a 4x, but will take an image from far further away than the "10x" zoom at 5-50mm.
For photography, focal length and sensor size is what matters. X numbers are just a marketing gimmick with no meaning, so x numbers are not used for higher end photography gear where it is expected those making purchases know that the x number is worthless. Without a starting focal length range the x number is completely meaningless as it tells you nothing about how big the camera will actually make things or how far away it can shoot from.