@reasonsat that seems like a big problem…and it underlies the even bigger problem of learning algebra and all sorts of topics without really understanding them.
For example, here is a very simple variant of the same problem that should all be easy to us now:
Q: If (4-x)/(2+x) = x, what is the value of x^2 + 3x - 28?
The same student wouldn’t be so lucky here because x^2 + 3x - 28 factors to (x-4)(x+7), but neither x = 4 nor x = -7 satisfy the first equation.
Instead, the first expression is equivalent to x^2 + 3x + 4 = 0. Now, the trick of seeing “oh hey there’s an x^2 + 3x here and there” becomes more apparent.