This is for a temperature mesurement aplication. The expression I'm trying to figure out using integer math is R2=R1/[(Vcc/V2)-1]. R2 is a thermistor. It changes it's internal resistence with temperature so i need to calculate it's resistence to figure out the temperature.

R1=10K
Vcc=5V
V2 is 0 to 4096 (quantisized output from a a/d converter); where 456=0.456V and 2345=2.345V
so the actual expression comes to:

R2=10.000/[(5000/ad_res)-1]

Code:
ad_res var word
temp0 var word
temp1 var word
temp2 var word
final1 var word
final2 var word
final3 var word

temp0=5000/ad_res
temp1=5000//ad_res
temp2=temp0*100+temp1-1
final1=10000/temp2
final2=10000//temp2
final3=final1*100+final2
overflow and imprecise result

VCC
o
|
# R1
#
|
|-------oV2
|
# R2
#
|
|
GND