Options: Combining skills:

If both tests pass, you succeed. If only one passes, partially pass as appropriate.

Example:
After a string of unlikely events, Salundra finds herself on-stage in yellow and red tights, singing and dancing in the Vargr Breughel Memorial Playhouse´s inaugural production of ´Tell Me On A Festag´. The GM calls for Challenging Perform (Dance) and Entertain (Sing) test, thinkin it unfair Salundra should have to enact each test in turn as it would significally reduce her overall chance of success.
Salundra has Perform (Dance) at 53, but doesn't have Entertain (Sing), so she must use her Fellowship of 43. She then rolls 46, meaning she managed the dance (+1 SL) but hit few off-notes with her singing (-0 SL) – not perfect, but good enough for gathered crowds; though Kym Neumann, the Altdorf Spieler's theatre critic, may not be writing a favorable review...