decryption problem with MD5

[zeytunak]

Hi

I have a string like "D9" with ascii code "44" for "D" and "39" for "9"
x=ascii(D)+ascii(9) ==> x=7D

I assume only uppercase char
in reverse 7D=44+39 ==>D9 ***
7D=45+38 ==>E8
7D=46+37 ==>F7


but in md5 we have 32 character that after adding them we have 16 key value like 7D in above example and every key value have 3 possibility ( i hope ) means we have 3*3*...*3=3^16= 43046721 posible string .

q1 : MD5 string have a special form to reduce above possible string ?

do you have an idea ho to reverse it ?

10x