havent seen this question asked

where do you come up with that...the only way the 300mm would be 10x is if it was a 30-300 where did you get 10x you have to start at 75mm or 70mm wich ever it is and dvied it.???

Not really. On a telescope or binocular, the system is design for direct viewing not projection onto a surface such as the focus screen. The "power" of the magnification is defined as the focal length of the primary lens system divided by the focal length of the eyepiece. Thus, my 900mm Meade reflecting telescope can be 100-power with a 9mm eyepiece, 200-power with a 4.5mm eyepiece, and 33-power with a 27mm eyepiece.

A 10-power binocular could achieve that power by using a 20mm eyepiece and a 200mm objective, or by using a 10mm eyepiece and a 100mm objective.

People tend to buy binoculars for their power (as above) and eye relief (diameter of the primary divided by the power), and telescopes for their light-gathering ability (diameter of the primary). We measure photographic lenses by their focal length and speed (which is the focal length divided by the primary diameter).

How much a given focal length of lens appears to magnify depends on how large the frame is. The reason we say a 300mm lens appears to magnify like a 10-power binocular with an APS sensor is that a normal lens, which appears not to magnify, is 30mm. What it means is that an object will be ten times bigger on the sensor with the 300 than with the 30. Since we define the normal lens as the diameter of the frame, you can get an idea of "power" by divided the focal length by the diameter of the frame.

Thus, a 300mm lens appears to be about 10 power on an APS sensor, 6.7-power on 35mm format, 3.75-power on 6x6 medium format, and so on.

But that doesn't mean it's the same as looking through a 10-power telescope. We look at the image on the focus screen thorugh a magnifier that is usually something like 4-power, meaning that it makes the screen appear four times bigger than if we just looked at it directly (as with an old twin-lens reflex camera). So, the apparent visual power depends on the focusing and viewing system in the camera, which has no effect on the image you produce.

Rick "noting a big perceptual difference between looking at an image projected onto a screen through a magnifying glass (as with a camera) and looking at a image projected onto your retina through an eyepiece" Denney

It's a matter of definitions. Your "X" is defined by you as the ratio of maximum to minimum focal length of a zoom lens. My "X" is defined as the ratio of the focal length to the diagonal of the frame. You can't look up "X" in a dictionary, so we just have to understand and define our usage so that people know what we are talking about.

Rick "thinking it's the idea, not the word, that gives a term its meaning" Denney

He's not talking about zoom range. He's saying that a 30mm lens (on a crop body) would give a 'natural' view, much like the scene would appear to the naked eye, therefore a 300mm lens would give a view like that afforded by 10x binoculars. As others have said, this has been debated many times, and you can argue that it is potentially misleading, but as long as you accept that the 30mm view is as the eye sees the scene, then the logic is sound.