[neal]

I was wondering if someone could help me figure out an equation for:

I want to scale a double (between 8-13) to be from 0 - 100.
So 8 will be 0, 9 will be 20, 13 will be 100, 12.5 will be 90 and so on.

I hope that makes sense and would appreciate if someone could help.

Thanks in advance!