By far the easiest way to Ghent is by train, a taxi will cost you a fortune (at least 100EUR). Once arrived in Brussels airport, the railway station is located under the airport itself at the -2 Floor. Note that there are:
direct fast trains to Ghent ('Gent Sint-Pieters') at least one every hour (< 1h)
direct stop trains from the airport to Ghent (> 1,5h)
non-direct trains whereby you need to change trains once in Brussel-Noord/Bruxelles-Nord (+/- 1h)
Walking from the station to the campus takes about 25 minutes. Follow Koning Albertlaan - Groot-Brittanniëlaan - Coupure Links.
By tram: tram nr. 4 or 24 will take you to the doorstep of the faculty. The tram will take about 10 minutes to get you to stop "Rozemarijnbrug". Cross the street and follow Coupure Links, which is the canal. The entrance of the campus is on the next corner.
by taxi: taxi's are parked at the front side of the station near the kiss-and-ride on -1 level, left when you exit the station. Taxi's are rather expensive.