How to make this?

Question

Payment Gateway site take:

3.99% + 0.25 cent

For Example: When my site get $600 the payment gateway take: 600-(600*0.0399)-0.25 = 575.81 and 600 - 575.81 = 24.19

How to reverse this Equation I mean 575.81 to 600

Thanks

Answer 1

You have $y= x-(x \cdot \frac{3.99}{100}+0.25)$

So to find $x$ given $y$ you find the inverse of the function.

$x = \dfrac{y+0.25}{1-\frac{3.99}{100}}$