Translation:How many universities and young men are in Philadelphia?
It would be nice if the examples weren't such that we have to type them over half a minute. Not to mention Roman places would fit better than American ones.
Anglophone accent. Check this channel for crystal clear pronunciation: https://www.youtube.com/channel/UCRllohBcHec7YUgW6HfltLA
It is sometimes locative (in Boston/in Philadelphia). Bostonia=Boston. Bostoniae=in Boston. Philadelphia=Philadelphia. Philadelphiae=in Philadelphia.
To make a city locative, -a becomes -ae, -us/-um becomes -i, thus:
Novum Eboracum=New York. Novi Eboraci=in New York.
The tips suggested that there may be exceptions, but that is the general rule for cities.
Duo doesn't mark misspellings as wrong unless the misspelled word turns into a word that already exists. You missed out the letter s from universities but that's ok. However, you wrote you men instead of young men" so that would be marked wrong because the word you" already exists and wouldn't be considered as a misspelling.