Question: Ok, we have two expressions:

> 
> $30x + 1500$  
> 
>  $19x + 9000$
> 
> 
> 

The first thing to note is, the first expression is $100\%$ and the second expression is $0\%$.

The second thing is to note in all of this is, $x$ is infinite in these expressions.

Ok, my main question is where would $23x + 15590$ go in the range as a percent? and how do you prove this? I don't know how but I'll accept any answer that makes sense. Bearing in mind $x$ is infinite, how?

Thank you though, I look forward to your answers.

EDIT: Hello guys, I apologize if that didn't make any sense. I meant in terms of this: [link](https://math.stackexchange.com/questions/51509/how-to-calculate-percentage-of-value-inside-arbitrary-range)

Answer: 
I guess you mean three values linearly dependent on $x$, say $f(x), g(x), h(x),$ the third one falling between the former two for $x$ big enough; and you are asking about an asymptotic value of the proportion
$$\frac{h-f}{g-f}$$
as $x$ grows to infinity.

That is
$$\begin{align}
\lim\_{x\to\infty}\frac{(23x+15590)-(19x+9000)}{(30x+1500)-(19x+9000)} &
 = \lim\_{x\to\infty}\frac{4x+6590}{11x-7500} \\
 & = \lim\_{x\to\infty}\frac{4+6590/x}{11-7500/x} \\
 & = \frac{4+0}{11-0} \\
 & = \frac 4{11} \\
 & \approx 0,363636 \\
 & \approx 36.4\%
\end{align}$$

For example, here are some values of the fraction defined above:  

for $x=10^3\ \,$ it is $\approx 3.025714286$,  

for $x=10^4\ \,$ it is $\approx 0.454536586$,  

for $x=10^8\ \,$ it is $\approx 0.363644834$ and  

for $x=10^{10}$ it is $\approx 0.363636448$.

But please note that the limit value as $x$ grows to infinity is **not** the same as a 'proportion of infinite values'! The former exists and can be calculated, the latter simply does not exist, is undefined.
Your objects are algebraic expressions. Among the possible interpretations are linear functions and straight lines in the plane. Interpreting them as linear functions would look like this:
$$
f(x) = 30x + 1500 \\
g(x) = 19x + 9000 \\
h(x) = 23x + 15590
$$

The only thing that makes remotely sense to me is that you have some interpolation problem. 
$$
\phi(1) = f \\
\phi(0) = g \\
\phi(\lambda) = h
$$
where $\phi$ is a map that maps a parameter $\lambda$ to some linear function. E.g.
$$
\phi(\lambda) = \lambda f + (1-\lambda) g
$$
would be such an interpolation. Alas your $h$ is probably not within the reachable functions of the above $\phi$.

Let us check it:
$$
\phi(\lambda) = \lambda(30x + 1500) + (1-\lambda)(19x +9000) \\
= (11 \lambda + 19) x + (9000 - 7500 \lambda)
$$
comparison with $h$ gives the conditions
$$
11 \lambda + 19 = 23 \\
9000 - 7500 \lambda = 15590
$$
or
$$
\lambda = 4/11 > 0 \\
\lambda = -6590/7500 < 0
$$
so there is no $\lambda \in \mathbb{R}$ which would result in $\phi(\lambda) = h$.