Just try Below query ,this is same as k_arumugam82 had sent,but bit modifications.
Select Curren.RegionName, Previous.Answer, Curren.Answer From
avg(D.Answer) as Answer
from Mst_Region B,
Voc_Trans_Details D where D.Month_Value=7 and D.Region_id=1 group by RegionName)as Curren JOIN
avg(C.Answer) as Answer
from Mst_Region A,
Voc_Trans_Details C where C.Month_Value=6 and A.Region_Id=1 group by RegionName) as Previous ON Curren.RegionName = Previous.RegionName