Question : Problem: difference between 20/4 and 24 pin power plugs to motherboard

My board has a place for a 24 pin plug
some power suppy has a w 20 pin plug.  
are they compatibile

Answer : Problem: difference between 20/4 and 24 pin power plugs to motherboard

Yes. A 20-pin connector will still fit in the board and the system will still work although you may not provide the necessary current for expansion slots etc.