Yes it is correct, however.

WHY do you think it is? What reasoning are you using to conjecture that that general case is always true? And the reason I ask is actually a VERY common problem that comes up among math learners, and that is believing that a pattern that they find is true.....pretty much just because. Don't get me wrong; math is all about recognizing patterns and formalizing them, and in that I think you have succeeded. But that's not enough; once you have what you think is a pattern, you want to be able to say WHY it's a pattern, and how you KNOW it always holds, or if it doesn't always hold, WHEN it holds.

In this case, it's real easy: you can multiply X on the Left Hand Side by 10/10 (since 10/10 = 1), note the common denominator, and add. And for something as simple as this, that sure feels like a hoop I'm just trying to make you jump through. But when the patterns get more complex and subtle, it'll get harder, but also more necessary, because your everyday intuitive pattern-matching won't cut it anymore.