How much weight can i loose and how?

Im startin school the 19th and right now how much weight can i loose by then like 3 weeks? any strict diets but not vegarian and i walk 1 1/2 mile evryday so where does that put me? im 170 rite now where will i be the 19th if i keep up with watever about leemme say 1200 calories a day!? help please no rediculos answers!