Mapping two values, suggestion for better formula

Question

Given values for original from 0 to 100, I need to calculate result where:

original = 0 corresponds to result = 2000

and

original = 200 corresponds to result = 200

Currently I am using this formula:

result = maxValue - (original * coefficient)

A simple example:

---

original    result    coefficient    maxValue
0           2000      18             2000
1           1982
2           1964      
3           1946      
4           1928
5           1910
6           1892
7           1874
8           1856
9           1838
10          1820
20          1640
80          560
90          380
91          362
92          344
93          326
94          308
95          290
96          272
97          254
98          236
99          218
100         200

---

I would like to know:

• a) If you could suggest me a different formula, please write an example and a brief simple term explanation.

• b) Which formula to use to find out original if I know only result (reverse), example for result = 1820, original should be 10 and so on.