Formula for variables of 2 points

[Apjow]

Hi, I need some help with a problem for programming a CNC equation. I'll try to explain as best as I can. I'm making doors and the hinges will vary depending on the length of door. One hinge will always be 7" from the top, another hinge will always be 9" from the bottom, 2 other hinges will be divided equally between the first 2.
LX=length of door(ex.96")
Hinge=3.5"
So, I know that the difference between the top and bottom hinges would be 73" and the difference between the middle hinges would be 22". What I need to know is a formula that would give me equal distances between the middle hinges no matter what the length of the door is.
I hope that explains it good enough.
Thanks for any help.
Apjow

 

[Dr.Peterson]

Between the top and bottom spaces and the four hinges, you've used up 7+9+4*3.5 = 30". That leaves 96 - 30 = 66" to be divided equally among the 3 remaining spaces. So each of them is 66/3 = 22".

Can you turn that into a formula?

 

[Apjow]

Between the top and bottom spaces and the four hinges, you've used up 7+9+4*3.5 = 30". That leaves 96 - 30 = 66" to be divided equally among the 3 remaining spaces. So each of them is 66/3 = 22".

Can you turn that into a formula?

So simple! Thank you very much!