Where is Solborg?

This map shows Solborg, which is about half way between Hønefoss and Jevnaker.

Getting to Solborg by bus.

There is a bus from Oslo Gardermoen airport to Solborg run by Askeladen tours: You can find the timetable here Askeladden Flybuss. 
The bus times are shown in the line that says "Avg. OSL pl 32". Ask the driver to stop at "Åsbygda Skole".

There are regular busses from Torp and Rygge ariports into Oslo center.
From Oslo centre, you need to take the bus to Hønefoss, then take another bus to Solborg .

The bus from Oslo Busterminal to Hønefoss Sentrum Stopp is the Brakar line 200. The timetable is also at reiseinfo.no line 200.
The buses from Hønefoss sentrum stopp to Solborg are the Brakar line 221 (Get off at "Åsbygda skole")