ADC calculation - help
Try changing this:
Temp = 680*((adc_result[6]-82)/(920-82));
To this:
Temp = 680L*(adc_result[6]-82)/(920-82);
or this:
Temp = (long)680*(adc_result[6]-82)/(920-82);
Notice that I removed the parens (as silvio explained), and I added "L" or "(long)" so the calculation uses long int instead of int (as artem explained). If your compiler conforms to the ANSI C standard, then long int is at least 32 bits, and that's plenty for this calculation.
If this stuff seems somewhat mysterious to you, try grabbing a good C programming book, and read the section on integer expression evaluation.