The South Circular Road is a long road curving around the south of the city, so different parts would be slightly different distances away. In general though it would be about 10 miles or 16 kilometres from Dublin Airport.
About 6 miles.
About 8 miles or 12 kilometres.
Stena Line goes from two places in Dublin. Dún Laoghaire, which is a port on south of the city is about 14 miles or 23 kilometres from Dublin Airport. There is also Dublin Port in the city, which is about 8 miles or 13 kilometres from Dublin Airport.
it takes 2 hours to drive from galway to Dublin
It is about 147 miles or 225 kilometres.
About 160 miles or 250 kilometres.
There is no actual place called the Dublin Exhibition Centre. There are a number of places in Dublin that have exhibitions, most notably the RDS (Royal Dublin Society). Dublin Airport is about 6 miles from the city centre. The RDS is about 2 miles from the city centre, on the opposite side than Dublin Airport. Most of the other places where they have exhibitions are close to the city too. So wherever the place you are referring to is, it is not far from Dublin Airport, within about 12 miles.
Blarney is in Cork, so to drive there from Dublin airport would take at least 3 hours on the motorway and could be more in heavy traffic.
From Roscommon town to Dublin Airport is about 100 miles or 162 kilometres. Depending on where specifically in the county of Roscommon you are going to, the distance would differ, but not by a large amount.
The distance between Portland airport and Seattle airport by road is 165.2 miles.
Dublin would be better. Shannon is just a town near Shannon Airport. Dublin is a city with many attractions, so there is far more to see and do.
At an absolute minimum, you might do it for €20. There are better options, as Dublin Airport is well served by buses which will bring you past Temple Bar for a far cheaper price. They might not bring you to exactly where you are going in Temple Bar, leaving you with a bit of a walk and you might have luggage, but it is a better option.