You can use the technology calculator for faster calculations, but here's how the time necessary for research can be calculated:
Basic time for research / 1 + 0,5 x University levels
The basic research time can be found when zero values are set to University and Academy of Sciences fields in the Technology calculator.
1) You better use brackets "(...)" in your formula
2) Still "Decreases by 0.5 times" is mathematical nonsense. You can't decrease something by less than 1
times.