Using public transit in Toronto, what is the quickest way from 1750 finch avenue east (Seneca) to brampton?

As stated in previous answer, take any route 39 bus west to Finch station. Unless you are travelling very early in the morning, however, you will have to take the subway south to York Mills to catch the GO bus to Brampton, as there are only two trips from Finch (at 0525 and 0610 on weekdays)